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:
Chemistry has ____ less important names.\Question: Choose the right answer from options given a) ten b) no c) eight d) nine

Ex Output:
b


Ex Input:
National immunization vaccinates all children under ____ against polio.\Question: Choose the right answer from options given a) zero b) four c) ten d) five

Ex Output:
b


Ex Input:
Stars live for billions of years and go through ____ basic stages.\Question: Choose the right answer from options given a) four b) seven c) zero d) five

Ex Output:

a