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: Islamic practice is based on what are called the ____ pillars of faith.\Question: Choose the right answer from options given a) eight b) one c) five d) four
Example Output: c

Example Input: Prairie voles look like rodents with small rounded bodies, ____ short legs and a short tail.\Question: Choose the right answer from options given a) two b) nine c) four d) zero
Example Output: c

Example Input: Neurological surgeons undergo ____ to eight years of rigorous training following medical school.\Question: Choose the right answer from options given a) six b) seven c) four d) five
Example Output:
a