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

Incubation is when birds keep their eggs warm while the embryos inside develop.
What is it called when birds keep their eggs warm while the embryos inside develop?

Photoautotrophs and chemoautotrophs are two basic types of autotrophs.
Photoautotrophs and chemoautotrophs are two basic types of what?

We call the worldwide radio-navigation system formed from a constellation of 24 satellites and their ground stations gps.
What do we call the worldwide radio-navigation system formed from a constellation of 24 satellites and their ground stations?