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

A visual "copy" of an object that is formed by reflected or refracted light is called image.
A visual "copy" of an object that is formed by reflected or refracted light is called what?

Socket secures teeth in the mouth.
What secures teeth in the mouth?

Helium-3 is produced by beta decay of a certain nuclide.
Helium-3 is produced by beta decay of a certain what?