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: Most children improve in three to ____ days.\Question: Choose the right answer from options given a) seven b) six c) four d) ten
Example Output: a

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: Plants can have ____ or more generations per season.\Question: Choose the right answer from options given a) two b) five c) four d) zero
Example Output:
a