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: Angiosperms inhabit all ____ continents, as well as the oceans.\Question: Choose the right answer from options given a) five b) seven c) three d) zero
Example Output: b

Example Input: Sports bras come in ____ basic styles.\Question: Choose the right answer from options given a) five b) six c) two d) zero
Example Output: c

Example Input: Mutations usually occur only once in every ____ million duplications of a DNA molecule.\Question: Choose the right answer from options given a) two b) ten c) five d) one
Example Output:
b