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:
Echinoderms usually have ____ appendages, but there are some exceptions.\Question: Choose the right answer from options given a) ten b) five c) seven d) three

Ex Output:
b


Ex Input:
Insects have ____ common types of metamorphosis.\Question: Choose the right answer from options given a) six b) eight c) two d) seven

Ex Output:
c


Ex Input:
Separation anxiety starts at approximately ____ monthe of age.\Question: Choose the right answer from options given a) nine b) one c) zero d) no

Ex Output:

a