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: 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: Stabilizers are also critical to operation of ____ point guidance systems.\Question: Choose the right answer from options given a) six b) no c) eight d) three
Example Output:
d