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: Ants have ____ stomachs.\Question: Choose the right answer from options given a) two b) nine c) four d) seven
Example Output: a

Example Input: Most viruses have only ____ organelles.\Question: Choose the right answer from options given a) ten b) two c) four d) eight
Example Output: b

Example Input: Clutches are useful in devices with ____ rotating shafts.\Question: Choose the right answer from options given a) two b) eight c) one d) seven
Example Output:
a