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: Gestation lasts ____ months, with the birth of a single calf.\Question: Choose the right answer from options given a) three b) one c) six d) eight
Example Output: d

Example Input: Amelia Island is the only territory in American history to serve under ____ flags.\Question: Choose the right answer from options given a) eight b) no c) six d) five
Example Output: a

Example Input: Viruses are the most common cause of acute asthma episodes in infants ____ months old or younger.\Question: Choose the right answer from options given a) nine b) ten c) six d) four
Example Output:
c