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: Cats have ____ lives.\Question: Choose the right answer from options given a) five b) one c) two d) nine
Example Output: d

Example Input: Background radiation comes from ____ sources.\Question: Choose the right answer from options given a) zero b) three c) four d) no
Example Output: b

Example Input: Calculators are great at giving numbers to ____ or twelve significant digits.\Question: Choose the right answer from options given a) eight b) ten c) four d) two
Example Output:
b