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: Scientists divide bats into ____ groups.\Question: Choose the right answer from options given a) five b) two c) one d) zero
Example Output: b

Example Input: Chipmunks produce one or ____ litters a year.\Question: Choose the right answer from options given a) three b) one c) ten d) two
Example Output: d

Example Input: Guinea pigs are rodents just like mice and hamsters, so they have only ____ long teeth.\Question: Choose the right answer from options given a) no b) four c) ten d) seven
Example Output:
b