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:
Some experts believe whining peaks around the ages of ____ or four.\Question: Choose the right answer from options given a) three b) no c) four d) seven

Ex Output:
a


Ex Input:
Reality is more than what can be perceived with the ____ senses.\Question: Choose the right answer from options given a) five b) four c) ten d) one

Ex Output:
a


Ex Input:
Some animals have only ____ or three chambers.\Question: Choose the right answer from options given a) no b) two c) six d) three

Ex Output:

b