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: Elephants have four molars, which are replaced ____ times, for a total of six sets in a lifetime.\Question: Choose the right answer from options given a) five b) no c) three d) one
Example Output: a

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

Example Input: Normal cells have ____ copies of each chromosome.\Question: Choose the right answer from options given a) two b) five c) eight d) no
Example Output:
a