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:
Echinoderms usually have ____ appendages, but there are some exceptions.\Question: Choose the right answer from options given a) ten b) five c) seven d) three

Ex Output:
b


Ex Input:
Calves are completely nutritionally dependent on their mothers to ____ months old.\Question: Choose the right answer from options given a) three b) zero c) five d) no

Ex Output:
a


Ex Input:
Kingsnakes usually mature within two to ____ years.\Question: Choose the right answer from options given a) three b) four c) zero d) seven

Ex Output:

a