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:
Motor neurons are divided into ____ groups.\Question: Choose the right answer from options given a) two b) six c) seven d) eight

Ex Output:
a


Ex Input:
Birds have ____ eyes.\Question: Choose the right answer from options given a) eight b) five c) nine d) two

Ex Output:
d


Ex Input:
Pelycosaurs are a paraphyletic group of ____ primitive families of synapsids.\Question: Choose the right answer from options given a) no b) one c) seven d) six

Ex Output:

d