This task is about creating an unanswerable question based on a given passage. Construct a question that looks relevant to the given context but is unanswerable. Following are a few suggestions about how to create unanswerable questions:
(i) create questions which require satisfying a constraint that is not mentioned in the passage
(ii) create questions which require information beyond what is provided in the passage in order to answer
(iii) replace an existing entity, number, date mentioned in the passage with other entity, number, date and use it in the question
(iv) create a question which is answerable from the passage and then replace one or two words by their antonyms or insert/remove negation words to make it unanswerable.

[EX Q]: Passage: The best, worst and average case complexity refer to three different ways of measuring the time complexity (or any other complexity measure) of different inputs of the same size. Since some inputs of size n may be faster to solve than others, we define the following complexities:
[EX A]: What are the three secondary expressions used to represent case complexity? 

[EX Q]: Passage: Labour went on to win the 1950 general election, but with a much reduced majority of five seats. Soon afterwards, defence became a divisive issue within the party, especially defence spending (which reached a peak of 14% of GDP in 1951 during the Korean War), straining public finances and forcing savings elsewhere. The Chancellor of the Exchequer, Hugh Gaitskell, introduced charges for NHS dentures and spectacles, causing Bevan, along with Harold Wilson (then President of the Board of Trade), to resign over the dilution of the principle of free treatment on which the NHS had been established.
[EX A]: In what year did Labour lose the general election?

[EX Q]: Passage: In February 2007, the U.S. Mint, under the Presidential $1 Coin Act of 2005, introduced a new $1 U.S. Presidential dollar coin. Based on the success of the "50 State Quarters" series, the new coin features a sequence of presidents in order of their inaugurations, starting with George Washington, on the obverse side. The reverse side features the Statue of Liberty. To allow for larger, more detailed portraits, the traditional inscriptions of "E Pluribus Unum", "In God We Trust", the year of minting or issuance, and the mint mark will be inscribed on the edge of the coin instead of the face. This feature, similar to the edge inscriptions seen on the British £1 coin, is not usually associated with U.S. coin designs. The inscription "Liberty" has been eliminated, with the Statue of Liberty serving as a sufficient replacement. In addition, due to the nature of U.S. coins, this will be the first time there will be circulating U.S. coins of different denominations with the same president featured on the obverse (heads) side (Lincoln/penny, Jefferson/nickel, Franklin D. Roosevelt/dime, Washington/quarter, Kennedy/half dollar, and Eisenhower/dollar). Another unusual fact about the new $1 coin is Grover Cleveland will have two coins with his portrait issued due to the fact he was the only U.S. President to be elected to two non-consecutive terms.
[EX A]:
In which year was the new Roosevelt Presidential coin introduced?