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

A vapor light produces visible light by electroluminescence process.
A vapor light produces visible light by what process?

The sun delivers power to the chemical factory chloroplasts.
What delivers power to the chemical factory chloroplasts?

The number of particles of a substance in a given volume is known as the concentration.

The number of particles of a substance in a given volume is known as?