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').

Input: Consider Input: Pups remain in the den for about ____ weeks, and are cared for by the entire pack.\Question: Choose the right answer from options given a) ten b) three c) six d) no

Output: c


Input: Consider Input: Cyclic neutropenia tends to occur every three weeks and last ____ to six days at a time.\Question: Choose the right answer from options given a) six b) four c) five d) three

Output: d


Input: Consider Input: Common irons is a mixture of ____ isotopes.\Question: Choose the right answer from options given a) one b) four c) five d) no


Output: b