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: Human feet bear average five to ____ hundreds tons of weight everyday.\Question: Choose the right answer from options given a) six b) eight c) five d) nine
Example Output: a

Example Input: Ozone is a naturally occurring molecule containing ____ atoms of oxygen.\Question: Choose the right answer from options given a) three b) five c) nine d) eight
Example Output: a

Example Input: Hex numbers have ____ digits.\Question: Choose the right answer from options given a) no b) seven c) six d) eight
Example Output:
c