Exhibit 4.2


 


THE REGISTERED HOLDER OF THIS PURCHASE
OPTION BY ITS ACCEPTANCE HEREOF AGREES THAT IT WILL NOT SELL, TRANSFER OR ASSIGN THIS PURCHASE OPTION EXCEPT AS HEREIN PROVIDED
AND THE REGISTERED HOLDER OF THIS PURCHASE OPTION AGREES THAT IT WILL NOT SELL, TRANSFER, ASSIGN, PLEDGE OR HYPOTHECATE THIS PURCHASE
OPTION OR CAUSE IT TO BE THE SUBJECT OF ANY HEDGING, SHORT SALE, DERIVATIVE, PUT, OR CALL TRANSACTION THAT WOULD RESULT IN THE
EFFECTIVE ECONOMIC DISPOSITION OF THE PURCHASE OPTION BY ANY PERSON FOR A PERIOD OF ONE HUNDRED EIGHTY DAYS FOLLOWING THE EFFECTIVE
DATE (AS DEFINED HEREIN) TO ANYONE OTHER THAN TO (I) CHARDAN CAPITAL MARKETS, LLC (“CHARDAN”) OR AN UNDERWRITER
OR SELECTED DEALER PARTICIPATING IN THE OFFERING OR (II) AN OFFICER OR PARTNER OF CHARDAN OR OF ANY SUCH UNDERWRITER OR SELECTED
DEALER AND IN ACCORDANCE WITH FINRA RULE 5110(G)(2).


 


THIS PURCHASE OPTION IS NOT EXERCISABLE
PRIOR TO THE LATER OF THE CONSUMMATION BY MOUNTAIN CREST ACQUISITION CORP (“COMPANY”) OF A MERGER, SHARE
EXCHANGE, ASSET ACQUISITION, RECAPITALIZATION, REORGANIZATION OR OTHER SIMILAR BUSINESS COMBINATION (“BUSINESS COMBINATION”)
(AS DESCRIBED MORE FULLY IN THE COMPANY’S REGISTRATION STATEMENT (DEFINED HEREIN)) AND DECEMBER 4, 2020. VOID AFTER 5:00
P.M. NEW YORK CITY LOCAL TIME, ON THE EARLIER OF THE LIQUIDATION OF THE COMPANY’S TRUST ACCOUNT (AS DESCRIBED IN THE REGISTRATION
STATEMENT) IF THE COMPANY HAS NOT COMPLETED A BUSINESS COMBINATION WITHIN THE REQUIRED TIME PERIODS OR JUNE 4, 20252.


 


UNIT PURCHASE OPTION

FOR THE PURCHASE OF

345,000 UNITS

OF

MOUNTAIN CREST ACQUISITION CORP


  


	1.	PURCHASE OPTION.


 


THIS CERTIFIES THAT, in consideration of
$100.00 duly paid by or on behalf of Chardan Capital Markets, LLC (“Holder”), as registered owner of
this Purchase Option, to Mountain Crest Acquisition Corp (“Company”), Holder is entitled, at any time
or from time to time upon the later of the consummation of a Business Combination or December 4, 20201 (“Commencement
Date”), and at or before 5:00 p.m., New York City local time, on the earlier of the liquidation of the Company’s
Trust Account (as described in the Company’s registration statement (“Registration Statement”)
pursuant to which Units are offered for sale to the public in the Company’s initial public offering (“Offering”))
in the event the Company has not completed a Business Combination within the required time periods and June 4, 2025, five years
from the effective date (“Effective Date”) of the Registration Statement (“Expiration Date”),
but not thereafter, to subscribe for, purchase and receive, in whole or in part, up to Three Hundred and Forty-Five Thousand (345,000)
units (“Units”) of the Company, each Unit consisting of one (1) share of common stock of the Company,
$0.0001 par value (“Common Stock”) and one (1) right to receive one-tenth (1/10) of a share of Common
Stock upon the consummation of a Business Combination (“Right(s)”). Each Right is the same as the right
included in the units being registered for sale to the public by way of the Registration Statement (“Public Rights”).
If the Expiration Date is a day on which banking institutions are authorized by law to close, then this Purchase Option may be
exercised on the next succeeding day which is not such a day in accordance with the terms herein. During the period ending on the
Expiration Date, the Company agrees not to take any action that would terminate the Purchase Option. This Purchase Option is initially
exercisable at $11.50 per Unit so purchased; provided, however, that upon the occurrence of any of the events specified
in Section 6 hereof, the rights granted by this Purchase Option, including the exercise price per Unit and the number of
Units (and Common Stock and Rights) to be received upon such exercise, shall be adjusted as therein specified. The term “Exercise
Price” shall mean the initial exercise price or the adjusted exercise price, depending on the context.


 






     


     


    

 


	2.	EXERCISE OF PURCHASE OPTION.


 


2.1         
Exercise Form. In order to exercise this Purchase Option, the exercise form attached hereto must be duly executed and completed
and delivered to the Company, together with this Purchase Option and payment of the Exercise Price for the Units being purchased
payable in cash or by certified check or official bank check. If the subscription rights represented hereby shall not be exercised
at or before 5:00 p.m., New York City local time, on the Expiration Date, this Purchase Option shall become and be void without
further force or effect, and all rights represented hereby shall cease and expire.


 


2.2         
Legend. Each certificate for the securities purchased under this Purchase Option shall bear a legend as follows, unless
such securities have been registered under the Securities Act of 1933, as amended (“Act”):


 


“The securities represented by this certificate have
not been registered under the Securities Act of 1933, as amended (“Act”) or applicable state law. The securities may
not be offered for sale, sold or otherwise transferred except pursuant to an effective registration statement under the Act, or
pursuant to an exemption from registration under the Act and applicable state law.”


 


2.3         
Cashless Exercise.


 


2.3.1      
Determination of Amount. In lieu of the payment of the Exercise Price multiplied by the number of Units for which this Purchase
Option is exercisable (and in lieu of being entitled to receive shares of Common Stock) in the manner required by Section 2.1,
and subject to Section 6.1 hereof, the Holder shall have the right (but not the obligation) to convert any exercisable but
unexercised portion of this Purchase Option into Units (“Cashless Exercise Right”) as follows: upon exercise
of the Cashless Exercise Right, the Company shall deliver to the Holder (without payment by the Holder of any of the Exercise Price
in cash) that number of Units (or that number of shares of Common Stock and Rights comprising that number of Units) equal to the
number of Units to be exercised multiplied by the quotient obtained by dividing (x) the “Value” (as defined below)
of the portion of the Purchase Option being converted by (y) the Current Market Value (as defined below). The “Value”
of the portion of the Purchase Option being converted shall equal the remainder derived from subtracting (a) (i) the Exercise Price
multiplied by (ii) the number of Units underlying the portion of this Purchase Option being converted from (b) the Current Market
Value of a Unit multiplied by the number of Units underlying the portion of the Purchase Option being converted. As used herein,
the term “Current Market Value” per Unit at any date means: (A) in the event that the Units, shares of
Common Stock and Public Rights are still trading, (i) if the Units are listed on a national securities exchange, the average reported
last sale price of the Units in the principal trading market for the Units as reported by the exchange, as the case may be, for
the three trading days preceding the date in question; or (ii) if the Units are not listed on a national securities exchange, but
are traded in the over-the-counter market, the average reported last sale price for Units for the three trading days preceding
the date in question for which such quotations are reported by the OTC Markets Group Inc., or similar publisher of such quotations;
(B) in the event that the Units are not still trading but the shares of Common Stock and Public Rights underlying the Units are
still trading, the aggregate of (i) the product of (x) the Current Market Price of the Common Stock and (y) the number of the shares
of Common Stock underlying one Unit (which shall include the portion of a share of Common Stock the holder of a Unit would automatically
receive in connection with the Right included in each such Unit); or (C) in the event that the Units are not still trading, the
aggregate of (i) the product of (x) the Current Market Price of the shares of Common Stock and (y) the number of the shares of
Common Stock underlying one Unit (which shall include the portion of a share of Common Stock the holder of a Unit would automatically
receive in connection with the Right included in each such Unit. The “Current Market Price” shall mean (i) if the Common
Stock is listed on a national securities exchange, the average reported last sale price of the Common Stock in the principal trading
market for the Common Stock as reported by the exchange for the three trading days preceding the date in question; (ii) if the
shares of Common Stock are not listed on a national securities exchange, but are traded in the over-the-counter market, the average
reported last sale price for the Common Stock for the three (3) trading days preceding the date in question for which such quotations
are reported by the OTC Markets Group Inc., or similar publisher of such quotations; and (iii) if the fair market value of the
shares of Common Stock cannot be determined pursuant to clause (i) or (ii) above, such price as the Board of Directors of the Company
shall determine, in good faith.


 









     


     


    

 


2.3.2      
Mechanics of Cashless Exercise. The Cashless Exercise Right may be exercised by the Holder on any business day on or after
the Commencement Date and not later than the Expiration Date by delivering the Purchase Option with the duly executed exercise
form attached hereto with the cashless exercise section completed to the Company, exercising the Cashless Exercise Right and specifying
the total number of Units the Holder will purchase pursuant to such Cashless Exercise Right.


 


2.4         
No Obligation to Net Cash Settle. Notwithstanding anything to the contrary contained in this Purchase Option, in no event
will the Company be required to net cash settle the exercise of the Purchase Option. The holder of the Purchase Option will not
be entitled to exercise the Purchase Option unless it exercises such Purchase Option pursuant to the Cashless Exercise Right or
a registration statement is effective, or an exemption from the registration requirements is available at such time and, if the
holder is not able to exercise the Purchase Option, the Purchase Option will expire worthless.


 


	3.	TRANSFER OF PURCHASE OPTION.


 


3.1         
General Restrictions. The registered Holder of this Purchase Option, by its acceptance hereof, agrees that it will not sell,
transfer, assign, pledge or hypothecate this Purchase Option (or the shares of Common Stock underlying this Purchase Option), or
cause the Purchase Option (or the shares of Common Stock underlying this Purchase Option) to be the subject of any hedging, short
sale, derivative, put, or call transaction that would result in the effective economic disposition of the Purchase Option by any
person, for a period of 180 days (pursuant to Rule 5110(g)(1) of the Conduct Rules of the Financial Industry Regulatory Authority
(FINRA)) following the Effective Date to anyone other than (i) Chardan or an underwriter or selected dealer in connection
with the Offering, or (ii) a bona fide officer or partner of Chardan or of any such underwriter or selected dealer. On and after
the 181st day following the Effective Date, transfers to others may be made subject to compliance with or exemptions from applicable
securities laws. In order to make any permitted assignment, the Holder must deliver to the Company the assignment form attached
hereto duly executed and completed, together with the Purchase Option and payment of all transfer taxes, if any, payable in connection
therewith. The Company shall within 5 business days transfer this Purchase Option on the books of the Company and shall execute
and deliver a new Purchase Option of like tenor to the appropriate assignee(s) expressly evidencing the right to purchase the aggregate
number of Units purchasable hereunder or such portion of such number as shall be contemplated by any such assignment.


 






     


     


    

 


3.2         
Restrictions Imposed by the Act. The securities evidenced by this Purchase Option shall not be transferred unless and until
(i) the Company has received the opinion of counsel for the Holder that the securities may be transferred pursuant to an exemption
from registration under the Act and applicable state securities laws, the availability of which is established to the reasonable
satisfaction of the Company (the Company hereby agreeing that the opinion of counsel for the Holder shall be deemed satisfactory
evidence of the availability of an exemption), or (ii) a registration statement or a post-effective amendment to the Registration
Statement relating to such securities has been filed by the Company and declared effective by the Securities and Exchange Commission
(the “Commission”) and compliance with applicable state securities law has been established.


 


	4.	NEW PURCHASE OPTION TO BE ISSUED.


 


4.1         
Partial Exercise or Transfer. Subject to the restrictions in Section 3 hereof, this Purchase Option may be exercised
or assigned in whole or in part. In the event of the exercise or assignment hereof in part only, upon surrender of this Purchase
Option for cancellation, together with the duly executed exercise or assignment form and funds sufficient to pay any Exercise Price
and/or transfer tax, the Company shall cause to be delivered to the Holder without charge a new Purchase Option of like tenor to
this Purchase Option in the name of the Holder evidencing the right of the Holder to purchase the number of Units purchasable hereunder
as to which this Purchase Option has not been exercised or assigned


 


4.2         
Lost Certificate. Upon receipt by the Company of evidence satisfactory to it of the loss, theft, destruction or mutilation
of this Purchase Option and of reasonably satisfactory indemnification or the posting of a bond, the Company shall execute and
deliver a new Purchase Option of like tenor and date. Any such new Purchase Option executed and delivered as a result of such loss,
theft, mutilation or destruction shall constitute a substitute contractual obligation on the part of the Company.


 


	5.	REGISTRATION RIGHTS.


 


5.1         
Demand Registration.


 


5.1.1    Grant of Right.
The Company, upon written demand (“Initial Demand Notice”) of the Holder(s) of at least 51% of the Purchase
Option and/or the underlying Units and/or the underlying securities (“Majority Holders”), agrees to use
its best efforts to register (the “Demand Registration”) under the Act on one occasion, all or any portion
of the (i) Purchase Option requested by the Majority Holders in the Initial Demand Notice and all of the securities underlying
such Purchase Option, including the Units and Common Stock and (ii) the units issued to the Holder prior to or concurrently with
the Offering and all the securities underlying such units (collectively, the “Registrable Securities”).
On such occasion, the Company will use its best efforts to file a registration statement or a post-effective amendment to the Registration
Statement covering the Registrable Securities as expeditiously as possible after receipt of the Initial Demand Notice and use its
best efforts to have such registration statement or post-effective amendment declared effective as soon as possible thereafter.
The demand for registration may be made at any time during a period of four and one-half years beginning 180 days after the Effective
Date. The Initial Demand Notice shall specify the number of shares of Registrable Securities proposed to be sold and the intended
method(s) of distribution thereof. The Company will notify all holders of the Purchase Option and/or Registrable Securities of
the demand within ten days from the date of the receipt of any such Initial Demand Notice. Each holder of Registrable Securities
who wishes to include all or a portion of such holder’s Registrable Securities in the Demand Registration (each such holder
including shares of Registrable Securities in such registration, a “Demanding Holder”) shall so notify
the Company within fifteen (15) days after the receipt by the holder of the notice from the Company. Upon any such request, the
Demanding Holders shall be entitled to have their Registrable Securities included in the Demand Registration, subject to Section
5.1.4. The Company shall not be required to effect more than one (1) Demand Registration under this Section 5.1 in respect
of all Registrable Securities.


 






     


     


    

 


5.1.2      
Effective Registration. Notwithstanding Section 5.1.5, a registration will not count as a Demand Registration until
the registration statement filed with the Commission, with respect to such Demand Registration, has been declared effective and
the Company has complied with all of its obligations under this Purchase Option with respect thereto.


 


5.1.3      
Underwritten Offering. If the Majority Holders so elect and such holders so advise the Company as part of the Initial Demand
Notice, the offering of such Registrable Securities pursuant to such Demand Registration shall be in the form of an underwritten
offering. In such event, the right of any holder to include its Registrable Securities in such registration shall be conditioned
upon such holder’s participation in such underwriting and the inclusion of such holder’s Registrable Securities in
the underwriting to the extent provided herein. All Demanding Holders proposing to distribute their securities through such underwriting
shall enter into an underwriting agreement in customary form with the underwriter or underwriters selected for such underwriting
by the Majority Holders.


 


5.1.4      
Reduction of Offering. If the managing underwriter or underwriters for a Demand Registration that is to be an underwritten
offering advises the Company and the Demanding Holders in writing that the dollar amount or number of shares of Registrable Securities
which the Demanding Holders desire to sell, taken together with all other shares of Common Stock or other securities which the
Company desires to sell and the shares of Common Stock, if any, as to which registration has been requested pursuant to written
contractual piggy-back registration rights held by other shareholders of the Company who desire to sell, exceeds the maximum dollar
amount or maximum number of shares that can be sold in such offering without adversely affecting the proposed offering price, the
timing, the distribution method, or the probability of success of such offering (such maximum dollar amount or maximum number of
shares, as applicable, the “Maximum Number of Shares”), then the Company shall include in such registration:
(i) first, the Registrable Securities as to which Demand Registration has been requested by the Demanding Holders (pro rata in
accordance with the number of shares that each such person has requested be included in such registration, regardless of the number
of shares held by each such person (such proportion is referred to herein as “Pro Rata”)) that can be
sold without exceeding the Maximum Number of Shares; (ii) second, to the extent that the Maximum Number of Shares has not been
reached under the foregoing clause (i), the shares of Common Stock or other securities that the Company desires to sell that can
be sold without exceeding the Maximum Number of Shares; (iii) third, to the extent that the Maximum Number of Shares has not been
reached under the foregoing clauses (i) and (ii), the shares of Common Stock or other securities registrable pursuant to the terms
of the Registration Rights Agreement between the Company and the initial investors in the Company, dated as of June 4, 2020 (the
 “Registration Rights Agreement” and such registrable securities, the “Investor Securities”)
as to which “piggy-back” registration has been requested by the holders thereof, Pro Rata, that can be sold without
exceeding the Maximum Number of Shares; and (iv) fourth, to the extent that the Maximum Number of Shares has not been reached under
the foregoing clauses (i), (ii), and (iii), the shares of Common Stock or other securities for the account of other persons that
the Company is obligated to register pursuant to written contractual arrangements with such persons and that can be sold without
exceeding the Maximum Number of Shares.


 


5.1.5      
Withdrawal. If a majority-in-interest of the Demanding Holders disapprove of the terms of any underwriting or are not entitled
to include all of their Registrable Securities in any offering, such majority-in-interest of the Demanding Holders may elect to
withdraw from such offering by giving written notice to the Company and the underwriter or underwriters of their request to withdraw
prior to the effectiveness of the registration statement filed with the Commission with respect to such Demand Registration. If
the majority-in-interest of the Demanding Holders withdraws from a proposed offering relating to a Demand Registration, then the
Company does not have to continue its obligations under Section 5.1, provided that, any such withdrawal will not
count as the Demand Registration if the Demanding Holders pay all of the Company’s out-of-pocket expenses, with respect to
such withdrawn registration.


 






     


     


    

 


5.1.6      
Terms. The Company shall bear all fees and expenses attendant to registering the Registrable Securities, including the expenses
of one legal counsel selected by the Holders to represent them in connection with the sale of the Registrable Securities, but the
Holders shall pay any and all underwriting commissions. The Company agrees to use its reasonable best efforts to qualify or register
the Registrable Securities in such states as are reasonably requested by the Majority Holder(s); provided, however,
that in no event shall the Company be required to register the Registrable Securities in a state in which such registration would
cause (i) the Company to be obligated to qualify to do business in such state, or would subject the Company to taxation as a foreign
corporation doing business in such jurisdiction or (ii) the principal shareholders of the Company to be obligated to escrow their
shares of capital stock of the Company. The Company shall use its best efforts to cause any registration statement or post-effective
amendment filed pursuant to the demand rights granted under Section 5.1.1 to remain effective for a period of nine consecutive
months from the effective date of such registration statement or post-effective amendment.


 


5.2         
Piggy-Back Registration.


 


5.2.1      
Piggy-Back Rights. If at any time during the seven year period commencing on the Effective Date the Company proposes to
file a registration statement under the Act with respect to an offering of equity securities, or securities or other obligations
exercisable or exchangeable for, or convertible into, equity securities, by the Company for its own account or for shareholders
of the Company for their account (or by the Company and by shareholders of the Company including, without limitation, pursuant
to Section 5.1), other than a registration statement (i) filed in connection with any employee stock option or other benefit
plan, (ii) for an exchange offer or offering of securities solely to the Company’s existing shareholders, (iii) for an offering
of debt that is convertible into equity securities of the Company or (iv) for a dividend reinvestment plan, then the Company shall
(x) give written notice of such proposed filing to the holders of Registrable Securities as soon as practicable but in no event
less than ten (10) days before the anticipated filing date, which notice shall describe the amount and type of securities to be
included in such offering, the intended method(s) of distribution, and the name of the proposed managing underwriter or underwriters,
if any, of the offering, and (y) offer to the holders of Registrable Securities in such notice the opportunity to register the
sale of such number of shares of Registrable Securities as such holders may request in writing within five (5) days following receipt
of such notice (a “Piggy-Back Registration”). The Company shall cause such Registrable Securities to
be included in such registration and shall use its best efforts to cause the managing underwriter or underwriters of a proposed
underwritten offering to permit the Registrable Securities requested to be included in a Piggy-Back Registration on the same terms
and conditions as any similar securities of the Company and to permit the sale or other disposition of such Registrable Securities
in accordance with the intended method(s) of distribution thereof. All holders of Registrable Securities proposing to distribute
their securities through a Piggy-Back Registration that involves an underwriter or underwriters shall enter into an underwriting
agreement in customary form with the underwriter or underwriters selected for such Piggy-Back Registration


 






     


     


    

 


5.2.2      
Reduction of Offering. If the managing underwriter or underwriters for a Piggy-Back Registration that is to be an underwritten
offering advises the Company and the holders of Registrable Securities in writing that the dollar amount or number of shares of
Common Stock which the Company desires to sell, taken together with the shares of Common Stock, if any, as to which registration
has been demanded pursuant to written contractual arrangements with persons other than the holders of Registrable Securities hereunder,
the Registrable Securities as to which registration has been requested under this Section 5.2, and the shares of Common
Stock, if any, as to which registration has been requested pursuant to the written contractual piggy-back registration rights of
other shareholders of the Company, exceeds the Maximum Number of Shares, then the Company shall include in any such registration:


 


(a)       
If the registration is undertaken for the Company’s account: (A) first, the shares of Common Stock or other securities that
the Company desires to sell that can be sold without exceeding the Maximum Number of Shares; (B) second, to the extent that the
Maximum Number of Shares has not been reached under the foregoing clause (A), the shares of Common Stock or other securities, if
any, comprised of Registrable Securities and Investor Securities, as to which registration has been requested pursuant to the applicable
written contractual piggy-back registration rights of such security holders, Pro Rata, that can be sold without exceeding the Maximum
Number of Shares; and (C) third, to the extent that the Maximum Number of shares has not been reached under the foregoing clauses
(A) and (B), the shares of Common Stock or other securities for the account of other persons that the Company is obligated to register
pursuant to written contractual piggy-back registration rights with such persons and that can be sold without exceeding the Maximum
Number of Shares;


 


(b)       
If the registration is a “demand” registration undertaken at the demand of holders of Investor Securities, (A) first,
the shares of Common Stock or other securities for the account of the demanding persons, Pro Rata, that can be sold without exceeding
the Maximum Number of Shares; (B) second, to the extent that the Maximum Number of Shares has not been reached under the foregoing
clause (A), the shares of Common Stock or other securities that the Company desires to sell that can be sold without exceeding
the Maximum Number of Shares; (C) third, to the extent that the Maximum Number of Shares has not been reached under the foregoing
clauses (A) and (B), the shares of Registrable Securities, Pro Rata, as to which registration has been requested pursuant to the
terms hereof, that can be sold without exceeding the Maximum Number of Shares; and (D) fourth, to the extent that the Maximum Number
of Shares has not been reached under the foregoing clauses (A), (B) and (C), the shares of Common Stock or other securities for
the account of other persons that the Company is obligated to register pursuant to written contractual arrangements with such persons,
that can be sold without exceeding the Maximum Number of Shares; and


 


(c)       
If the registration is a “demand” registration undertaken at the demand of persons other than either the holders of
Registrable Securities or of Investor Securities, (A) first, the shares of Common Stock or other securities for the account of
the demanding persons that can be sold without exceeding the Maximum Number of Shares; (B) second, to the extent that the Maximum
Number of Shares has not been reached under the foregoing clause (A), the shares of Common Stock or other securities that the Company
desires to sell that can be sold without exceeding the Maximum Number of Shares; (C) third, to the extent that the Maximum Number
of Shares has not been reached under the foregoing clauses (A) and (B), collectively the shares of Common Stock or other securities
comprised of Registrable Securities and Investor Securities, Pro Rata, as to which registration has been requested pursuant to
the terms hereof and of the Registration Rights Agreement, as applicable, that can be sold without exceeding the Maximum Number
of Shares; and (D) fourth, to the extent that the Maximum Number of Shares has not been reached under the foregoing clauses (A),
(B) and (C), the shares of Common Stock or other securities for the account of other persons that the Company is obligated to register
pursuant to written contractual arrangements with such persons, that can be sold without exceeding the Maximum Number of Shares.


 






     


     


    

 


5.2.3      
Withdrawal. Any holder of Registrable Securities may elect to withdraw such holder’s request for inclusion of Registrable
Securities in any Piggy-Back Registration by giving written notice to the Company of such request to withdraw prior to the effectiveness
of the registration statement. The Company (whether on its own determination or as the result of a withdrawal by persons making
a demand pursuant to written contractual obligations) may withdraw a registration statement at any time prior to the effectiveness
of the registration statement. Notwithstanding any such withdrawal, the Company shall pay all expenses incurred by the holders
of Registrable Securities in connection with such Piggy-Back Registration as provided in Section 5.2.4.


 


5.2.4      
Terms. The Company shall bear all fees and expenses attendant to registering the Registrable Securities, including the expenses
of one legal counsel selected by the Holders to represent them in connection with the sale of the Registrable Securities but the
Holders shall pay any and all underwriting commissions related to the Registrable Securities. In the event of such a proposed registration,
the Company shall furnish the then Holders of outstanding Registrable Securities with not less than fifteen days written notice
prior to the proposed date of filing of such registration statement. Such notice to the Holders shall continue to be given for
each applicable registration statement filed (during the period in which the Purchase Option is exercisable) by the Company until
such time as all of the Registrable Securities have been registered and sold. The Holders of the Registrable Securities shall exercise
the “piggy-back” rights provided for herein by giving written notice within ten days of the receipt of the Company’s
notice of its intention to file a registration statement. The Company shall use its best efforts to cause any registration statement
filed pursuant to the above “piggyback” rights to remain effective for at least nine months from the date that the
Holders of the Registrable Securities are first given the opportunity to sell all of such securities.


 


5.3         
General Terms.


 


5.3.1    Indemnification.
The Company shall indemnify the Holder(s) of the Registrable Securities to be sold pursuant to any registration statement hereunder
and each person, if any, who controls such Holders within the meaning of Section 15 of the Act or Section 20(a) of the Securities
Exchange Act of 1934, as amended (“Exchange Act”), against all loss, claim, damage, expense or liability
(including all reasonable attorneys’ fees and other expenses reasonably incurred in investigating, preparing or defending
against litigation, commenced or threatened, or any claim whatsoever whether arising out of any action between the underwriter
and the Company or between the underwriter and any third party or otherwise) to which any of them may become subject under the
Act, the Exchange Act or otherwise, arising from such registration statement but only to the same extent and with the same effect
as the provisions pursuant to which the Company has agreed to indemnify the underwriters contained in Section 5 of the Underwriting
Agreement between the Company, Chardan and the other underwriters named therein dated the Effective Date (“Underwriting
Agreement”). The Holder(s) of the Registrable Securities to be sold pursuant to such registration statement, and
their successors and assigns, shall severally, and not jointly, indemnify the Company, its officers and directors and each person,
if any, who controls the Company within the meaning of Section 15 of the Act or Section 20(a) of the Exchange Act, against all
loss, claim, damage, expense or liability (including all reasonable attorneys’ fees and other expenses reasonably incurred
in investigating, preparing or defending against any claim whatsoever) to which they may become subject under the Act, the Exchange
Act or otherwise, arising from information furnished by or on behalf of such Holders, or their successors or assigns for specific
inclusion in such registration statement or arising from any omission or the alleged omission to state a material fact required
to be stated therein or necessary to make the statement contained therein not misleading in connection with the registration of
the Registrable Securities, to the same extent and with the same effect as the provisions contained in Section 5 of the Underwriting
Agreement pursuant to which the underwriters have agreed to indemnify the Company.


 









     


     


    

 


5.3.2      
Exercise of Purchase Option. Nothing contained in this Purchase Option shall be construed as requiring the Holder(s) to
exercise their Purchase Option prior to or after the initial filing of any registration statement or the effectiveness thereof.


 


5.3.3      
Documents Delivered to Holders. The Company shall furnish Chardan, for as long as it is a Holder, as representative of the
Holders participating in any of the foregoing offerings, a signed counterpart, addressed to the participating Holders, of (i) an
opinion of counsel to the Company, dated the effective date of such registration statement (and, if such registration includes
an underwritten public offering, an opinion dated the date of the closing under any underwriting agreement related thereto), and
(ii) a “cold comfort” letter dated the effective date of such registration statement (and, if such registration includes
an underwritten public offering, a letter dated the date of the closing under the underwriting agreement) signed by the independent
public accountants who have issued a report on the Company’s financial statements included in such registration statement,
in each case covering substantially the same matters with respect to such registration statement (and the prospectus included therein)
and, in the case of such accountants’ letter, with respect to events subsequent to the date of such financial statements,
as are customarily covered in opinions of issuer’s counsel and in accountants’ letters delivered to underwriters in
underwritten public offerings of securities. The Company shall also deliver promptly to Chardan, as representative of the Holders
participating in the offering, the correspondence and memoranda described below and copies of all correspondence between the Commission
and the Company, its counsel or auditors and all memoranda relating to discussions with the Commission or its staff with respect
to the registration statement and permit Chardan, as representative of the Holders, to do such investigation, upon reasonable advance
notice, with respect to information contained in or omitted from the registration statement as it deems reasonably necessary to
comply with applicable securities laws or rules of FINRA. Such investigation shall include access to books, records and properties
and opportunities to discuss the business of the Company with its officers and independent auditors, all to such reasonable extent
and at such reasonable times and as often as Chardan, as representative of the Holders, shall reasonably request. The Company shall
not be required to disclose any confidential information or other records to Chardan, as representative of the Holders, or to any
other person, until and unless such persons shall have entered into reasonable confidentiality agreements (in form and substance
reasonably satisfactory to the Company), with the Company with respect thereto.


 


5.3.4      
Underwriting Agreement. The Company shall enter into an underwriting agreement with the managing underwriter(s), if any,
selected by any Holders whose Registrable Securities are being registered pursuant to this Section 5, which managing underwriter
shall be reasonably acceptable to the Company. Such agreement shall be reasonably satisfactory in form and substance to the Company,
each Holder and such managing underwriters, and shall contain such representations, warranties and covenants by the Company and
such other terms as are customarily contained in agreements of that type used by the managing underwriter. The Holders shall be
parties to any underwriting agreement relating to an underwritten sale of their Registrable Securities and may, at their option,
require that any or all the representations, warranties and covenants of the Company to or for the benefit of such underwriters
shall also be made to and for the benefit of such Holders. Such Holders shall not be required to make any representations or warranties
to or agreements with the Company or the underwriters except as they may relate to such Holders and their intended methods of distribution.
Such Holders, however, shall agree to such covenants and indemnification and contribution obligations for selling shareholders
as are customarily contained in agreements of that type used by the managing underwriter. Further, such Holders shall execute appropriate
custody agreements and otherwise cooperate fully in the preparation of the registration statement and other documents relating
to any offering in which they include securities pursuant to this Section 5. Each Holder shall also furnish to the Company such
information regarding itself, the Registrable Securities held by it, and the intended method of disposition of such securities
as shall be reasonably required to effect the registration of the Registrable Securities.


 






     


     


    

 


5.3.5      
Rule 144 Sale. Notwithstanding anything contained in this Section 5 to the contrary, the Company shall have no obligation
pursuant to Sections 5.1 or 5.2 to use its best efforts to obtain the registration of Registrable Securities held
by any Holder (i) where such Holder would then be entitled to sell under Rule 144 within any three-month period (or such other
period prescribed under Rule 144 as may be provided by amendment thereof) all of the Registrable Securities then held by such Holder,
or (ii) where the number of Registrable Securities held by such Holder is within the volume limitations under paragraph (e) of
Rule 144 (calculated as if such Holder were an affiliate within the meaning of Rule 144).


 


5.3.6      
Supplemental Prospectus. Each Holder agrees, that upon receipt of any notice from the Company of the happening of any event
as a result of which the prospectus included in the registration statement, as then in effect, includes an untrue statement of
a material fact or omits to state a material fact required to be stated therein or necessary to make the statements therein not
misleading in light of the circumstances then existing, such Holder will immediately discontinue disposition of Registrable Securities
pursuant to the registration statement covering such Registrable Securities until such Holder’s receipt of the copies of
a supplemental or amended prospectus, and, if so desired by the Company, such Holder shall deliver to the Company (at the expense
of the Company) or destroy (and deliver to the Company a certificate of such destruction) all copies, other than permanent file
copies then in such Holder’s possession, of the prospectus covering such Registrable Securities current at the time of receipt
of such notice.


 


	6.	ADJUSTMENTS.


 


6.1         
Adjustments to Exercise Price and Number of Securities. The Exercise Price and the number of Units underlying the Purchase
Option shall be subject to adjustment from time to time as hereinafter set forth:


 


6.1.1      
Stock Dividends - Split-Ups. If after the date hereof, and subject to the provisions of Section 6.3 below, the number
of outstanding shares of Common Stock is increased by a stock dividend payable in shares of Common Stock or by a split-up of Common
Stock or other similar event, then, on the effective date thereof, the number of shares of Common Stock underlying each of the
Units purchasable hereunder shall be increased in proportion to such increase in outstanding shares.


 


6.1.2      
Aggregation of Shares. If after the date hereof, and subject to the provisions of Section 6.3, the number of outstanding
shares of Common Stock is decreased by a consolidation, combination or reclassification of Common Stock or other similar event,
then, on the effective date thereof, the number of shares of Common Stock underlying each of the Units purchasable hereunder shall
be decreased in proportion to such decrease in outstanding shares and the Exercise Price shall be proportionately increased.


 


6.1.3      
Replacement of Securities upon Reorganization, etc. In case of any reclassification or reorganization of the outstanding
shares of Common Stock other than a change covered by Section 6.1.1 or 6.1.2 hereof or that solely affects the par
value of such shares of Common Stock, or in the case of any merger or consolidation of the Company with or into another company
(other than a consolidation or merger in which the Company is the continuing entity and that does not result in any reclassification
or reorganization of the outstanding shares of Common Stock), or in the case of any sale or conveyance to another company or entity
of the property of the Company as an entirety or substantially as an entirety in connection with which the Company is dissolved,
the Holder of this Purchase Option shall have the right thereafter (until the expiration of the right of exercise of this Purchase
Option) to receive upon the exercise hereof, for the same aggregate Exercise Price payable hereunder immediately prior to such
event, the kind and amount of shares or other securities or property (including cash) receivable upon such reclassification, reorganization,
merger or consolidation, or upon a dissolution following any such sale or transfer, by a Holder of the number of shares of Common
Stock of the Company obtainable upon exercise of this Purchase Option immediately prior to such event; and if any reclassification
also results in a change in shares of Common Stock covered by Section 6.1.1 or 6.1.2, then such adjustment shall
be made pursuant to Sections 6.1.1, 6.1.2 and this Section 6.1.3. The provisions of this Section 6.1.3
shall similarly apply to successive reclassifications, reorganizations, mergers or consolidations, sales or other transfers.


 






     


     


    

 


6.1.4      
Changes in Form of Purchase Option. This form of Purchase Option need not be changed because of any change pursuant to this
Section, and a Purchase Option issued after such change may state the same Exercise Price and the same number of Units as are stated
in the Purchase Option as initially issued. The acceptance by any Holder of the issuance of a new Purchase Option reflecting a
required or permissive change shall not be deemed to waive any rights to an adjustment occurring after the Commencement Date or
the computation thereof.


 


6.2         
Substitute Purchase Option. In case of any consolidation of the Company with, or merger of the Company with, or merger of
the Company into, another entity (other than a consolidation or merger which does not result in any reclassification or change
of the outstanding shares of Common Stock), the entity formed by such consolidation or merger shall execute and deliver to the
Holder a supplemental Purchase Option providing that the holder of each Purchase Option then outstanding or to be outstanding shall
have the right thereafter (until the stated expiration of such Purchase Option) to receive, upon exercise of such Purchase Option,
the kind and amount of shares and other securities and property receivable upon such consolidation or merger, by a holder of the
number of shares of Common Stock of the Company for which such Purchase Option might have been exercised immediately prior to such
consolidation, merger, sale or transfer. Such supplemental Purchase Option shall provide for adjustments which shall be identical
to the adjustments provided in Section 6. The above provision of this Section shall similarly apply to successive consolidations
or mergers.


 


6.3         
Elimination of Fractional Interests. The Company shall not be required to issue certificates representing fractions of Common
Stock upon the exercise of the Purchase Option, nor shall it be required to issue scrip or pay cash in lieu of any fractional interests,
it being the intent of the parties that all fractional interests shall be eliminated by rounding any fraction up or down to the
nearest whole number of Common Stock or other securities, properties or rights.


 


7.            
RESERVATION AND LISTING. The Company shall at all times reserve and keep available out of its authorized but unissued shares
of Common Stock, solely for the purpose of issuance upon exercise of the Purchase Option (including the shares of Common Stock
underlying the Rights), such number of shares of Common Stock or other securities, properties or rights as shall be issuable upon
the exercise thereof. The Company covenants and agrees that, upon exercise of the Purchase Option and payment of the Exercise Price
therefore, all shares of Common Stock and other securities issuable upon such exercise shall be duly and validly issued, fully
paid and non-assessable and not subject to preemptive rights of any shareholder. As long as the Purchase Option shall be outstanding,
the Company shall use its best efforts to cause all (i) Units and shares of Common Stock issuable upon exercise of the Purchase
Option, (ii) Rights issuable upon exercise of the Purchase Option and (iii) shares of Common Stock underlying the Rights included
in the Units issuable upon exercise of the Purchase Option to be listed and/or quoted (subject to official notice of issuance)
on all securities exchanges (or, if applicable, on the OTC Bulletin Board or OTC Markets Group, Inc. or any successor trading market)
on which the Common Stock may then be listed and/or quoted.


 






     


     


    

 


	8.	CERTAIN NOTICE REQUIREMENTS.


 


8.1         
Holder’s Right to Receive Notice. Nothing herein shall be construed as conferring upon the Holders the right to vote
or consent as a shareholders for the election of directors or any other matter, or as having any rights whatsoever as a shareholders
of the Company. If, however, at any time prior to the expiration of the Purchase Option and its exercise, any of the events described
in Section 8.2 shall occur, then, in each such event, the Company shall give written notice of such event at least fifteen
days prior to the date fixed as a record date or the date of closing the transfer books for the determination of the shareholders
entitled to such dividend, distribution, conversion or exchange of securities or subscription rights, or entitled to vote on such
proposed dissolution, liquidation, winding up or sale. Such notice shall specify such record date or the date of the closing of
the transfer books, as the case may be. Notwithstanding the foregoing, the Company shall deliver to each Holder a copy of each
notice given to the other shareholders of the Company at the same time and in the same manner that such notice is given to the
shareholders.


 


8.2         
Events Requiring Notice. The Company shall be required to give the notice described in this Section 8 upon one or more of
the following events: (i) if the Company shall take a record of the holders of its shares of Common Stock for the purpose of entitling
them to receive a dividend or distribution payable otherwise than in cash, or a cash dividend or distribution payable otherwise
than out of retained earnings, as indicated by the accounting treatment of such dividend or distribution on the books of the Company,
or (ii) the Company shall offer to all the holders of its shares of Common Stock any additional shares of capital stock of the
Company or securities convertible into or exchangeable for shares of capital stock of the Company, or any option, right or warrant
to subscribe therefor, or (iii) a dissolution, liquidation or winding up of the Company (other than in connection with a consolidation
or merger) or a sale of all or substantially all of its property, assets and business shall be proposed.


 


8.3         
Notice of Change in Exercise Price. The Company shall, promptly after an event requiring a change in the Exercise Price
pursuant to Section 6 hereof, send notice to the Holders of such event and change (“Price Notice”). The
Price Notice shall describe the event causing the change and the method of calculating same and shall be certified as being true
and accurate by the Company’s Chief Executive Officer.


 


8.4         
Transmittal of Notices. All notices, requests, consents and other communications under this Purchase Option shall be in
writing and shall be deemed to have been duly made when hand delivered, or mailed by express mail or private courier service: (i)
if to the registered Holder of the Purchase Option, to the address of such Holder as shown on the books of the Company, or (ii)
if to the Company, to the following address or to such other address as the Company may designate by notice to the Holders:


 


Mountain Crest Acquisition Corp.


311 West 43rd Street


12th Floor


New York, New York 10036


Attn: Suying Liu


Telephone: (646) 493-6558


 


	9.	MISCELLANEOUS.


 


9.1      
Amendment The Company and Chardan, for as long as it is a Holder, may from time to time supplement or amend this Purchase
Option without the approval of any of the Holders in order to cure any ambiguity, to correct or supplement any provision contained
herein that may be defective or inconsistent with any other provisions herein, or to make any other provisions in regard to matters
or questions arising hereunder that the Company and Chardan may deem necessary or desirable and that the Company and Chardan deem
shall not adversely affect the interest of the Holders. All other modifications or amendments shall require the written consent
of and be signed by the party against whom enforcement of the modification or amendment is sought.


 






     


     


    

 


9.2         
Headings. The headings contained herein are for the sole purpose of convenience of reference, and shall not in any way limit
or affect the meaning or interpretation of any of the terms or provisions of this Purchase Option.


 


9.3         
Entire Agreement. This Purchase Option (together with the other agreements and documents being delivered pursuant to or
in connection with this Purchase Option) constitutes the entire agreement of the parties hereto with respect to the subject matter
hereof, and supersedes all prior agreements and understandings of the parties, oral and written, with respect to the subject matter
hereof.


 


9.4         
Binding Effect. This Purchase Option shall inure solely to the benefit of and shall be binding upon the Holder and the Company
and their permitted assignees, respective successors, legal representative and assigns, and no other person shall have or be construed
to have any legal or equitable right, remedy or claim under or in respect of or by virtue of this Purchase Option or any provisions
herein contained.


 


9.5         
Governing Law; Submission to Jurisdiction. This Purchase Option shall be governed by and construed and enforced in accordance
with the laws of the State of New York, without giving effect to conflict of laws principles thereof. Each of the Holder and the
Company hereby agrees that any action, proceeding or claim against it arising out of, or relating in any way to this Purchase Option
shall be brought and enforced in the New York Supreme Court, County of New York, or in the United States District Court for the
Southern District of New York, and irrevocably submits to such jurisdiction, which jurisdiction shall be exclusive. Each of the
Holder and the Company hereby waives any objection to such exclusive jurisdiction and that such courts represent an inconvenient
forum. Any process or summons to be served upon the Company may be served by transmitting a copy thereof by registered or certified
mail, return receipt requested, postage prepaid, addressed to it at the address set forth in Section 8.4 hereof. Such mailing
shall be deemed personal service and shall be legal and binding upon the Company in any action, proceeding or claim. The Company
and the Holder agree that the prevailing party(ies) in any such action shall be entitled to recover from the other party(ies) all
of its reasonable attorneys’ fees and expenses relating to such action or proceeding and/or incurred in connection with the
preparation therefore.


 


9.6         
Waiver, Etc. The failure of the Company or the Holder to at any time enforce any of the provisions of this Purchase Option
shall not be deemed or construed to be a waiver of any such provision, nor to in any way affect the validity of this Purchase Option
or any provision hereof or the right of the Company or any Holder to thereafter enforce each and every provision of this Purchase
Option. No waiver of any breach, non-compliance or non-fulfillment of any of the provisions of this Purchase Option shall be effective
unless set forth in a written instrument executed by the party or parties against whom or which enforcement of such waiver is sought;
and no waiver of any such breach, non-compliance or non- fulfillment shall be construed or deemed to be a waiver of any other or
subsequent breach or non-compliance.


 


9.7         
Execution in Counterparts. This Purchase Option may be executed in one or more counterparts, and by the different parties
hereto in separate counterparts, each of which shall be deemed to be an original, but all of which taken together shall constitute
one and the same agreement, and shall become effective when one or more counterparts has been signed by each of the parties hereto
and delivered to each of the other parties hereto.


 






     


     


    

 


9.8         
Exchange Agreement. As a condition of the Holder’s receipt and acceptance of this Purchase Option, Holder agrees that,
at any time prior to the complete exercise of this Purchase Option by Holder, if the Company and Chardan enter into an agreement
(“Exchange Agreement”) pursuant to which they agree that all outstanding Purchase Option’s will
be exchanged for securities or cash or a combination of both, then Holder shall agree to such exchange and become a party to the
Exchange Agreement.


 


[Signature Page Follows]


 









     


     


    

 


IN WITNESS WHEREOF, the Company has caused this Purchase Option
to be signed by its duly authorized officer as of the 4th day of June, 2020.


 


	 	MOUNTAIN CREST ACQUISITION CORP
	 	 
	 	By:	 /s/ Suying Liu
	 	 	Name: Suying Liu
	 	 	 
	 	 	Title:  Chief Executive Officer


 






     


     


    

 


Form to be used to exercise Purchase
Option


 


Mountain Crest Acquisition Corp


311 West 43rd Street


12th Floor


New York, New York 10036


Attn: Suying Liu


 


Date:_________________, 20___


 


The undersigned hereby elects irrevocably
to exercise all or a portion of the within Purchase Option and to purchase ____ Units of Mountain Crest Acquisition Corp and hereby
makes payment of $____________ (at the rate of $_________ per Unit) in payment of the Exercise Price pursuant thereto. Please issue
the securities as to which this Purchase Option is exercised in accordance with the instructions given below.


 


or


 


The undersigned hereby elects irrevocably
to convert its right to purchase _________ Units purchasable under the within Purchase Option by surrender of the unexercised portion
of the attached Purchase Option (with a “Value” based of $_______ based on a “Market Price” of $_______).
Please issue the securities comprising the Units as to which this Purchase Option is exercised in accordance with the instructions
given below.


 


________________________


 


NOTICE:  The signature to this assignment
must correspond with the name as written upon the face of the purchase option in every particular, without alteration or enlargement
or any change whatever


 


Signature(s) Guaranteed:


 


THE SIGNATURE(S) SHOULD BE GUARANTEED BY
AN ELIGIBLE GUARANTOR INSTITUTION (BANKS, STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS AND CREDIT UNIONS WITH MEMBERSHIP IN AN APPROVED
SIGNATURE GUARANTEE MEDALLION PROGRAM, PURSUANT TO S.E.C. RULE 17Ad-15).


 






     


     


    

 


INSTRUCTIONS FOR REGISTRATION OF SECURITIES


 


Name


 


	 
	(Print in Block Letters)


 


Address


 


	 


 






     


     


    

 


Form to be used to assign Purchase Option:


 


ASSIGNMENT


 


(To be executed by the registered Holder
to effect a transfer of the within Purchase Option):


 


FOR VALUE RECEIVED,______________________________________________
does hereby sell, assign and transfer unto___________________________________________ the right to purchase __________ Units of
Mountain Crest Acquisition Corp (“Company”) evidenced by the within Purchase Option and does hereby authorize
the Company to transfer such right on the books of the Company.


 


Dated:___________________, 20__


 


	 	 	 
	 	Signature


 


	 	 	 
	 	NOTICE:  The signature to this assignment must correspond with the name as written upon the face of the purchase option in every particular, without alteration or enlargement or any change whatever.


 


Signature(s) Guaranteed:


 


THE SIGNATURE(S) SHOULD
BE GUARANTEED BY AN ELIGIBLE GUARANTOR INSTITUTION (BANKS, STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS AND CREDIT UNIONS WITH MEMBERSHIP
IN AN APPROVED SIGNATURE GUARANTEE MEDALLION PROGRAM, PURSUANT TO S.E.C. RULE 17Ad-15).