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

Example Input: Scorpions also have ____ legs.\Question: Choose the right answer from options given a) eight b) zero c) nine d) ten
Example Output: a

Example Input: Knives have ____ cutting edges each.\Question: Choose the right answer from options given a) zero b) nine c) two d) ten
Example Output:
c