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: Today there are ____ UK hospitals doing heart transplants.\Question: Choose the right answer from options given a) three b) five c) six d) nine
Example Output: d

Example Input: Rapid growth occurs for the first ____ years of life.\Question: Choose the right answer from options given a) eight b) ten c) three d) five
Example Output: d

Example Input: Calanoid copepods are only ____ millimeters long and eat phytoplankton, or plant plankton.\Question: Choose the right answer from options given a) seven b) five c) three d) two
Example Output:
c