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: Rabbits reach sexual maturity between three and ____ months of age.\Question: Choose the right answer from options given a) three b) seven c) six d) zero
Example Output: c

Example Input: Sound waves travel through the air in a similar manner, but in all ____ dimensions.\Question: Choose the right answer from options given a) three b) five c) nine d) one
Example Output: a

Example Input: Today there are still ____ billion people without electricity.\Question: Choose the right answer from options given a) no b) two c) five d) eight
Example Output:
b