Given a scientific passage and an answer, generate a question for the given answer.

Q: Passage: Opposite charges attract, and like charges repel. Answer: attract

A: What do opposite charges do to one another?
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Q: Passage: Did you ever have a picnic ruined by a surprise rainstorm? People often complain when the weather forecast is wrong. But in fact, weather forecasts today are much more accurate than they were just 20 years ago. Scientists who study and forecast the weather are called meteorologists . How do they predict the weather?. Answer: meteorologists

A: What do we call scientists who study and forecast the weather?
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Q: Passage: Stratus clouds occur low in the troposphere. They form in layers that spread horizontally and may cover the entire sky like a thick blanket. Stratus clouds that produce precipitation are called nimbostratus. The prefix nimbo- means "rain. ". Answer: low

A:
Where do stratus clouds occur in the troposphere?
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