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: Collars come in ____ shapes.\Question: Choose the right answer from options given a) six b) two c) four d) zero
Example Output: b

Example Input: Circumcisions usually heal within ____ to two weeks.\Question: Choose the right answer from options given a) one b) five c) eight d) nine
Example Output: a

Example Input: Vision problems affect one in ____ school-aged children.\Question: Choose the right answer from options given a) six b) four c) seven d) one
Example Output:
b