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: Diarrheal disease kills ____ million children every year.\Question: Choose the right answer from options given a) three b) no c) four d) ten
Example Output: a

Example Input: Earwigs produce ____ or two generations every year.\Question: Choose the right answer from options given a) two b) no c) one d) nine
Example Output: c

Example Input: Fish have ____ different musculature systems for swimming.\Question: Choose the right answer from options given a) nine b) ten c) zero d) two
Example Output:
d