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: Background radiation comes from ____ sources.\Question: Choose the right answer from options given a) zero b) three c) four d) no

A: b
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Q: Ozone is a molecule containing ____ oxygen atoms.\Question: Choose the right answer from options given a) one b) nine c) no d) three

A: d
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Q: Hibernation occurs for about ____ months.\Question: Choose the right answer from options given a) eight b) seven c) one d) five

A:
b
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