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:
Dunes are of ____ types - linear and parabolic.\Question: Choose the right answer from options given a) three b) four c) ten d) two

Ex Output:
d


Ex Input:
Microwave ovens emit ____ kinds of radiation.\Question: Choose the right answer from options given a) six b) two c) four d) eight

Ex Output:
b


Ex Input:
Teeth develop from ____ embryonic tissues.\Question: Choose the right answer from options given a) two b) six c) five d) zero

Ex Output:

a