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').

Example Input: Some sources claim there are more like ____ million vertebrate animals in zoos.\Question: Choose the right answer from options given a) six b) five c) one d) three
Example Output: b

Example Input: Gasoline is ____ times as expensive as in the United States.\Question: Choose the right answer from options given a) two b) four c) three d) ten
Example Output: c

Example Input: Anorexics see the world as black and white, and ____ shades of gray.\Question: Choose the right answer from options given a) three b) five c) two d) no
Example Output:
d