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: Most people recover in one to ____ months.\Question: Choose the right answer from options given a) no b) three c) seven d) eight
Example Output: b

Example Input: Motor neurons are divided into ____ groups.\Question: Choose the right answer from options given a) two b) six c) seven d) eight
Example Output: a

Example Input: Air pollution kills ____ million more.\Question: Choose the right answer from options given a) nine b) no c) eight d) three
Example Output:
d