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: All mass spectrometers consist of ____ distinct regions.\Question: Choose the right answer from options given a) three b) one c) two d) zero
Example Output: a

Example Input: Humans normally produce only ____ sets of teeth.\Question: Choose the right answer from options given a) nine b) eight c) two d) three
Example Output: c

Example Input: Democracy is ____ wolves and one sheep voting on what to have for supper.\Question: Choose the right answer from options given a) ten b) three c) zero d) one
Example Output:
b