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: Onion thrips experience ____ instars.\Question: Choose the right answer from options given a) three b) six c) eight d) four
Example Output: d

Example Input: Water softeners add sodium to drinking water in ____ ways.\Question: Choose the right answer from options given a) zero b) six c) two d) nine
Example Output: c

Example Input: Recent studies show obesity is up ____ percent over the past year.\Question: Choose the right answer from options given a) ten b) six c) one d) zero
Example Output:
b