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: 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: Psychiatrists say that one in ____ people are mentally ill.\Question: Choose the right answer from options given a) one b) two c) four d) nine
Example Output: c

Example Input: Beak sculpture consists of five or ____ distinct angled ridges.\Question: Choose the right answer from options given a) eight b) ten c) no d) six
Example Output:
d