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: Vision problems affect one in ____ school-aged children.\Question: Choose the right answer from options given a) six b) four c) seven d) one

A: b
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Q: Songbirds have ____ sets of vocal chords.\Question: Choose the right answer from options given a) six b) two c) eight d) ten

A: b
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Q: Most walkers do walk at least half an hour at a time, but fewer walk ____ or more times a week.\Question: Choose the right answer from options given a) no b) two c) zero d) four

A:
d
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