Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

Q: Some compounds form rigid frameworks called crystals.

A: Some compounds form rigid frameworks called what?
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Q: The climate is defined as the temperature plus precipitation of an area over a long period of time.

A: What is defined as the temperature plus precipitation of an area over a long period of time?
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Q: Birds evolved from reptile ancestors.

A:
Birds evolved from what type of ancestor?
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