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:
Reptiles also have scaly skin and a ____ chambered heart.\Question: Choose the right answer from options given a) zero b) one c) ten d) three

Ex Output:
d


Ex Input:
Children now account for only ____ percent of all forest fires caused in the United States.\Question: Choose the right answer from options given a) five b) four c) eight d) nine

Ex Output:
b


Ex Input:
Manatees reach sexual maturity in ____ to five years.\Question: Choose the right answer from options given a) two b) no c) seven d) four

Ex Output:

a