Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
--------
Question: Incubation is when birds keep their eggs warm while the embryos inside develop.

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


Question: Photoautotrophs and chemoautotrophs are two basic types of autotrophs.

Answer: Photoautotrophs and chemoautotrophs are two basic types of what?


Question: Water is an oxide of hydrogen.

Answer:
Water is an oxide of what element?