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?

10 million years long can a large star be on the main sequence stage.
How long can a large star be on the main sequence stage?

Stem basic structure holds plants upright, bears leaves and other structures, and transports fluids between roots and leaves.
What basic structure holds plants upright, bears leaves and other structures, and transports fluids between roots and leaves?