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:
All mass spectrometers consist of ____ distinct regions.\Question: Choose the right answer from options given a) three b) one c) two d) zero

Ex Output:
a


Ex Input:
Diarrheal disease kills ____ million children every year.\Question: Choose the right answer from options given a) three b) no c) four d) ten

Ex Output:
a


Ex Input:
Reservoirs are of ____ general types nonpressurized and pressurized.\Question: Choose the right answer from options given a) ten b) two c) no d) seven

Ex Output:

b