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:
Elephants give birth to one calf every ____ to nine years on average.\Question: Choose the right answer from options given a) no b) four c) three d) seven

Ex Output:
b


Ex Input:
Calves can swim ____ days after they are born.\Question: Choose the right answer from options given a) ten b) two c) zero d) one

Ex Output:
b


Ex Input:
Hyperactive children become magnesium deficient for ____ reasons.\Question: Choose the right answer from options given a) zero b) no c) two d) one

Ex Output:

c