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:
Carbon can bond to a maximum of ____ atoms.\Question: Choose the right answer from options given a) six b) ten c) five d) four

Ex Output:
d


Ex Input:
Utility theory expresses the decision makers' preferences on a scale from ____ to one.\Question: Choose the right answer from options given a) eight b) three c) zero d) no

Ex Output:

c