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: Pandas reach adulthood at about ____ years of age.\Question: Choose the right answer from options given a) eight b) seven c) five d) six
Example Output: c

Example Input: All butterflies go through ____ life stages .\Question: Choose the right answer from options given a) one b) four c) zero d) five
Example Output: b

Example Input: Mitotic activity is usually minimal and there is ____ necrosis or vascular invasion.\Question: Choose the right answer from options given a) seven b) four c) no d) two
Example Output:
c