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:
Reverse osmosis uses three to ____ gallons of water to produce one gallon of drinking water.\Question: Choose the right answer from options given a) six b) eight c) five d) ten

Ex Output:
d


Ex Input:
Most people have ____ kidneys.\Question: Choose the right answer from options given a) two b) five c) seven d) six

Ex Output:
a


Ex Input:
Females usually reach sexual maturity at about four years of age, males at about ____ years.\Question: Choose the right answer from options given a) six b) seven c) two d) five

Ex Output:

a