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: Some skulls show the marks of up to ____ bullets.\Question: Choose the right answer from options given a) five b) three c) eight d) six
Example Output: d

Example Input: Female cats come into heat cycles every ____ to four weeks during certain times of the year.\Question: Choose the right answer from options given a) eight b) ten c) zero d) three
Example Output: d

Example Input: Young trees can make ____ feet of growth in a single season.\Question: Choose the right answer from options given a) six b) zero c) no d) four
Example Output:
a