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 have four molars, which are replaced ____ times, for a total of six sets in a lifetime.\Question: Choose the right answer from options given a) five b) no c) three d) one

Ex Output:
a


Ex Input:
Pistillate flowers have a compound ovary with ____ locules topped by three sticky, sessile stigmas.\Question: Choose the right answer from options given a) zero b) three c) six d) seven

Ex Output:
b


Ex Input:
Most ichthyologists currently consider the char to be ____ species.\Question: Choose the right answer from options given a) no b) one c) three d) two

Ex Output:

d