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:
Antibodies contain ____ pairs of protein chains.\Question: Choose the right answer from options given a) no b) two c) nine d) zero

Ex Output:
b


Ex Input:
Coffee trees reach maturity between ____ and four years when their clusters of fruit turn deep red.\Question: Choose the right answer from options given a) no b) three c) nine d) five

Ex Output:
b


Ex Input:
Spacecraft starting from the surface of Earth has a ____ initial speed .\Question: Choose the right answer from options given a) three b) one c) zero d) four

Ex Output:

c