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: Embrasures have ____ functions.\Question: Choose the right answer from options given a) three b) seven c) zero d) nine
Example Output: a

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: Bacteriophage lambda has ____ different life cycles.\Question: Choose the right answer from options given a) nine b) two c) five d) ten
Example Output:
b