Given a sentence with a missing word, pick the answer option that best fills out the missing word in the sentence. Indicate each answer with its index ('a', 'b', 'c', 'd').

Example Input: Smallmouth bass grow to ____ inches in their first growing season.\Question: Choose the right answer from options given a) five b) four c) seven d) ten
Example Output: a

Example Input: Vaccinated newborns have protection for at least ____ years.\Question: Choose the right answer from options given a) four b) five c) two d) no
Example Output: b

Example Input: Personal computers used for businesses generally originate from ____ sources today.\Question: Choose the right answer from options given a) four b) eight c) one d) three
Example Output:
a