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

Ex Output:
d


Ex Input:
Dunes are of ____ types - linear and parabolic.\Question: Choose the right answer from options given a) three b) four c) ten d) two

Ex Output:
d


Ex Input:
Exports support one out of every ____ manufacturing jobs in the United States.\Question: Choose the right answer from options given a) zero b) two c) five d) eight

Ex Output:

c