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: Ground squirrels breed once a year, averaging ____ to eight per litter.\Question: Choose the right answer from options given a) seven b) one c) six d) ten
Example Output: a

Example Input: Kabbalists group the simple letters into ____ triplets.\Question: Choose the right answer from options given a) four b) no c) ten d) three
Example Output: a

Example Input: Diabetics are three to ____ times more at risk for heart attack.\Question: Choose the right answer from options given a) ten b) two c) four d) seven
Example Output:
d