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:
Ground squirrels breed once a year, averaging ____ to eight per litter.\Question: Choose the right answer from options given a) seven b) one c) six d) ten

Ex Output:
a


Ex Input:
Nymphs emerge in ____ to seven days and flatten themselves against the leaf to feed.\Question: Choose the right answer from options given a) one b) five c) nine d) two

Ex Output:
b


Ex Input:
Pacific leatherbacks divide into ____ populations.\Question: Choose the right answer from options given a) seven b) four c) ten d) two

Ex Output:

d