Given a scientific question, generate a correct answer to it.

[Q]: What is formed when water vapor in the air condenses into tiny droplets?
[A]: fog

[Q]: Adding the number of protons plus the number of neutrons in an atom, decides it's approximate mass, what is another word for this value?
[A]: atomic number

[Q]: Deserts and forests are examples of what type of biome?
[A]:
terrestrial