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: Most gerbils live three to ____ years and have few health problems.\Question: Choose the right answer from options given a) three b) four c) seven d) zero
Example Output: b

Example Input: Ankle joint has ____ degrees of freedom.\Question: Choose the right answer from options given a) seven b) eight c) four d) three
Example Output: d

Example Input: International groups promote safe sex and ____ population growth.\Question: Choose the right answer from options given a) two b) six c) ten d) zero
Example Output:
d