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: Respiratory therapists complete two to ____ years of education.\Question: Choose the right answer from options given a) no b) one c) four d) eight
Example Output: c

Example Input: Ants have ____ noses.\Question: Choose the right answer from options given a) zero b) eight c) five d) three
Example Output: c

Example Input: Blood cells remain in circulation for ____ to three months.\Question: Choose the right answer from options given a) two b) one c) three d) nine
Example Output:
a