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

Q: Mucous does the esophagus produce for lubrication.

A: What does the esophagus produce for lubrication?
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Q: In science, something that always applies under the same conditions is called a scientific law.

A: In science, what do you call something that always applies under the same conditions?
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Q: Transforming from a caterpillar to a butterfly requires a lot of energy.

A:
Transforming from a caterpillar to a butterfly requires a lot of what?
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