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: 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: Many people have ____ symptoms until they suffer chest pains or a heart attack.\Question: Choose the right answer from options given a) three b) one c) no d) seven
Example Output: c

Example Input: Natural molybdenum contains ____ isotopes.\Question: Choose the right answer from options given a) zero b) five c) two d) seven
Example Output:
d