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: Blood pressure is measured by ____ numbers.\Question: Choose the right answer from options given a) zero b) eight c) two d) seven
Example Output: c

Example Input: Humans normally produce only ____ sets of teeth.\Question: Choose the right answer from options given a) nine b) eight c) two d) three
Example Output: c

Example Input: Pain medications ease the discomfort which can last for up to ____ days.\Question: Choose the right answer from options given a) zero b) three c) ten d) seven
Example Output:
d