Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
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Question: Mesoderm type of cell layer do flatworms have.

Answer: What type of cell layer do flatworms have?


Question: Wave amplitude and wavelength are two important measures of wave size.

Answer: Wave amplitude and wavelength are two important measures of what?


Question: Most of food's chemical energy ultimately comes from sunlight.

Answer:
Most of food's chemical energy ultimately comes from what source?