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

Phosphate groups are found within phospholipids and nucleotides.
Phosphate groups are found within phospholipids and what else?

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.
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?

Electrons in the outer energy level of an atom are called valence electrons.
What are electrons in the outer energy level of an atom called?