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: Astronomers fall in ____ classes - professionals and amateurs.\Question: Choose the right answer from options given a) two b) four c) six d) zero

Output: a


Input: Consider Input: Uncontrolled diabetes can increase risk by up to ____ times.\Question: Choose the right answer from options given a) five b) four c) seven d) eight

Output: b


Input: Consider Input: Blue crabs have ____ pairs of walking legs and paddle-shaped rear swimming legs.\Question: Choose the right answer from options given a) no b) two c) three d) six

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
Output: c


