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:
Vision disorders affect ____ in every four school-age children.\Question: Choose the right answer from options given a) nine b) one c) five d) six

Ex Output:
b


Ex Input:
Birds have ____ eyes.\Question: Choose the right answer from options given a) eight b) five c) nine d) two

Ex Output:
d


Ex Input:
Centipedes are born with as few as ____ pairs of legs, gaining a new set with each molting.\Question: Choose the right answer from options given a) four b) five c) ten d) eight

Ex Output:

a