Question

which factor produced most of the oxygen that is found in the atmosphere today?
outgassing
living organisms
photodissociation
condensation

Explanation:

Living organisms, especially plants and algae, produce oxygen through photosynthesis. Outgassing releases gases from the Earth's interior but not significant oxygen. Photodissociation is a minor source. Condensation is related to water vapor, not oxygen production.

Answer:

living organisms