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: Pelicans use ____ different ways to feed.\Question: Choose the right answer from options given a) no b) nine c) one d) two
Example Output: d

Example Input: Brachiopods are superficially similar to bivalves, both having ____ shells.\Question: Choose the right answer from options given a) two b) eight c) seven d) one
Example Output: a

Example Input: Inevitability is both grace and ____ ground, the fuel of fate, the fire of fortune.\Question: Choose the right answer from options given a) zero b) two c) six d) ten
Example Output:
a