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

Q: Diffusion process helps absorptive protists absorb food molecules across their cell membranes.

A: Which process helps absorptive protists absorb food molecules across their cell membranes?
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Q: A penguin must do increase muscle mass before molting.

A: A penguin must do what before molting?
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Q: In science, motion is defined as a change in position.

A:
In science, what is defined as a change in position?
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