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').

Ex Input:
Calves remain hidden for much of the time, and are weaned by ____ months of age.\Question: Choose the right answer from options given a) six b) three c) eight d) one

Ex Output:
b

Ex Input:
Condors become sexually mature at about five or ____ years of age and mate for life.\Question: Choose the right answer from options given a) nine b) seven c) one d) six

Ex Output:
d

Ex Input:
Trees grow rapidly, often three to ____ feet or more in a single growing season.\Question: Choose the right answer from options given a) no b) one c) four d) five

Ex Output:
c