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: Anthrax usually is a fatal disease with ____ symptoms observed.\Question: Choose the right answer from options given a) no b) seven c) one d) six
Example Output: a

Example Input: Evolution is dependent on ____ forces.\Question: Choose the right answer from options given a) no b) five c) two d) seven
Example Output: c

Example Input: Meerkats are gregarious and have at least ____ distinctive vocalizations.\Question: Choose the right answer from options given a) eight b) ten c) one d) six
Example Output:
b