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:
Tetrapods are animals that have ____ legs or leg-like appendages.\Question: Choose the right answer from options given a) four b) one c) ten d) six

Ex Output:
a


Ex Input:
Ants have ____ distinct body parts.\Question: Choose the right answer from options given a) nine b) zero c) no d) three

Ex Output:
d


Ex Input:
Nouns occur in ____ forms, primary and secondary.\Question: Choose the right answer from options given a) three b) two c) four d) ten

Ex Output:

b