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: 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: Cleavage occurs typically in either one, two, three, four, or ____ directions.\Question: Choose the right answer from options given a) six b) three c) ten d) two
Example Output: a

Example Input: Insects have six legs, two antennae, and ____ body sections.\Question: Choose the right answer from options given a) three b) nine c) one d) eight
Example Output:
a