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: Some skulls show the marks of up to ____ bullets.\Question: Choose the right answer from options given a) five b) three c) eight d) six
Example Output: d

Example Input: Perennial grass takes ____ to five years before it is mature enough to produce adequate seed.\Question: Choose the right answer from options given a) six b) zero c) three d) no
Example Output: c

Example Input: Mountain goats have ____ sharp horns.\Question: Choose the right answer from options given a) two b) six c) ten d) four
Example Output:
a