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 endocrinologists see patients every ____ months throughout the pregnancy.\Question: Choose the right answer from options given a) six b) two c) zero d) three

Ex Output:
b


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