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: 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: Firebrat eggs hatch in about ____ weeks.\Question: Choose the right answer from options given a) ten b) one c) two d) no
Example Output: c

Example Input: Scorpions live in warmer habitats than spiders and can live ____ or five months without food.\Question: Choose the right answer from options given a) one b) ten c) five d) four
Example Output:
d