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

On a global scale, plants and other photosynthetic organisms have generated all of the oxygen in the air.
On a global scale, plants and other photosynthetic organisms have generated all of what element in the air?

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

The amount of energy required to begin a chemical reaction is known as the activation energy.

What is the amount of energy required to begin a chemical reaction known as?