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').

Ex Input:
Chemical interactions are essentially electron interactions of ____ atoms.\Question: Choose the right answer from options given a) six b) no c) ten d) two

Ex Output:
d


Ex Input:
Coccidiosis usually occurs from ____ weeks of age.\Question: Choose the right answer from options given a) zero b) no c) three d) eight

Ex Output:
c


Ex Input:
Autism is a developmental disability that often appears during the first ____ years of life.\Question: Choose the right answer from options given a) nine b) three c) ten d) two

Ex Output:

b