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').

Q: Most children experience at least one episode by the time they are ____ years old.\Question: Choose the right answer from options given a) eight b) one c) ten d) seven

A: d
****
Q: Astronauts sleep only ____ hours each night, on average.\Question: Choose the right answer from options given a) six b) one c) four d) seven

A: a
****
Q: Many women have ____ to five abortions during their life time.\Question: Choose the right answer from options given a) nine b) zero c) five d) four

A:
d
****