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: Circles mark the approximate locations of ____ recently discovered solar systems.\Question: Choose the right answer from options given a) four b) no c) zero d) nine
Example Output: a

Example Input: Infection can cause a range of illnesses, from ____ symptoms to fatal disease.\Question: Choose the right answer from options given a) no b) four c) six d) one
Example Output:
a