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: Cows have four stomachs, and the first ____ yield merchantable tripe.\Question: Choose the right answer from options given a) two b) five c) zero d) three
Example Output: d

Example Input: Most infected persons have ____ symptoms of disease.\Question: Choose the right answer from options given a) six b) no c) three d) one
Example Output: b

Example Input: Ferromagnetic objects have the strongest magnetic force out of the ____ magnetic types.\Question: Choose the right answer from options given a) two b) three c) one d) six
Example Output:
b