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: Human rabies is extremely rare, and there have been no cases in Oregon in the last ____ years.\Question: Choose the right answer from options given a) nine b) five c) ten d) eight
Example Output: d

Example Input: Takins can even balance on their hind hooves to nibble on vegetation ____ feet above ground.\Question: Choose the right answer from options given a) two b) no c) nine d) eight
Example Output: d

Example Input: Most astronauts sleep for just ____ hours.\Question: Choose the right answer from options given a) six b) ten c) five d) two
Example Output:
a