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

Q: Endoscopes are used to explore the body through various orifices or minor incisions.

A: Endoscopes are used to explore the body through various orifices or these?
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Q: Momentum is directly related to both mass and velocity.

A: Momentum is directly related to both mass and?
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Q: Remains unchanged happens to the mass number during a nuclear decay process by positron emission.

A:
What happens to the mass number during a nuclear decay process by positron emission?
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