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: Prairie voles look like rodents with small rounded bodies, ____ short legs and a short tail.\Question: Choose the right answer from options given a) two b) nine c) four d) zero
Example Output: c

Example Input: Reservoirs cover an area of the planet ____ times the size of Britain.\Question: Choose the right answer from options given a) two b) eight c) three d) six
Example Output: d

Example Input: Newborns have irregular sleep cycles that take about ____ months to mature.\Question: Choose the right answer from options given a) six b) ten c) nine d) seven
Example Output:
a