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

Q: A student should use a balance to compare the masses of two small rocks.

A: Which tool should a student use to compare the masses of two small rocks?
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Q: Microevolution is the process by which organisms change in small ways over time.

A: What is the process by which organisms change in small ways over time?
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Q: Expanding gas gas pressure-forces are used to move an object the work is done on the object by.

A:
When gas pressure-forces are used to move an object the work is done on the object by?
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