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

Q: While the numerical aperture can be used to compare resolutions of various objectives, it does not indicate how far the lens could be from the specimen.

A: While the numerical aperture can be used to compare resolutions of various objectives, it does not indicate how far the lens could be from the what?
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Q: On a global scale, plants and other photosynthetic organisms have generated all of the oxygen in the air.

A: On a global scale, plants and other photosynthetic organisms have generated all of what element in the air?
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Q: Depth and density are the two factors that affect the pressure of fluids.

A:
What are the two factors that affect the pressure of fluids?
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