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: Vampires generally are male, and rabies is ____ times more frequent in men than in women.\Question: Choose the right answer from options given a) no b) two c) zero d) seven
Example Output: d

Example Input: Astronomical observations suggest ____ or close to zero space-time curvature.\Question: Choose the right answer from options given a) six b) zero c) ten d) seven
Example Output: b

Example Input: Salt prints are the most modern of the ____ photographic processes.\Question: Choose the right answer from options given a) six b) three c) two d) seven
Example Output:
b