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: Humans normally produce only ____ sets of teeth.\Question: Choose the right answer from options given a) nine b) eight c) two d) three

A: c
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Q: Midrange drivers are used in multi-way speakers with ____ or more driver sizes.\Question: Choose the right answer from options given a) one b) five c) four d) three

A: d
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Q: Ventilation uses ____ physical properties of air to be effective.\Question: Choose the right answer from options given a) five b) six c) three d) two

A:
d
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