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: 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: Embryos develop and hatch in about four weeks, then spend four to ____ months in the tadpole stage.\Question: Choose the right answer from options given a) five b) nine c) eight d) two
Example Output: a

Example Input: Tadpoles use shallow waters near shore for at least ____ months while completing development.\Question: Choose the right answer from options given a) no b) six c) nine d) ten
Example Output:
b