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

[EX Q]: Opaque is the term for matter that does not let any light pass through.
[EX A]: What is the term for matter that does not let any light pass through?

[EX 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.
[EX 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?

[EX Q]: Rock stata is stacked in layers in "layer cake geology".
[EX A]:
What is stacked in layers in "layer cake geology"?