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: Embryos develop and hatch in about four weeks, then spend four to ____ months in the tadpole stage.\Question: Choose the right answer from options given a) five b) nine c) eight d) two
Example Output: a

Example Input: Female cats have ____ X's in each cell.\Question: Choose the right answer from options given a) five b) two c) one d) ten
Example Output: b

Example Input: Smoking is responsible for one in ____ deaths in the United States.\Question: Choose the right answer from options given a) five b) eight c) no d) two
Example Output:
a