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

Q: 10 million years long can a large star be on the main sequence stage.

A: How long can a large star be on the main sequence stage?
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Q: The pupil is the name of the black opening in the eye that lets light enter.

A: What is the name of the black opening in the eye that lets light enter?
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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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