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

The reverse process of moving material into a cell is the process of exocytosis.
The reverse process of moving material into a cell is the process of what?

Atoms of metals are good conductors of electricity because they give up electrons.
Why are atoms of metals good conductors of electricity?

Reduced family size is the key to the demographic transition.

What is the key to the demographic transition?