The presence of oxygen in Earth's atmosphere is thought to result directly from what type of process?
A) volcanic eruptions
B) outgassing of the oceans
C) original condensation of interplanetary gas clouds
D) biological activity of plants and animals

Question

Quizplus · Accepted Answer

The presence of oxygen in Earth's atmosphere is primarily attributed to the process of photosynthesis, which is a biological activity performed by plants and certain microorganisms. These organisms convert carbon dioxide and water into oxygen and glucose, thereby releasing oxygen into the atmosphere.

The Presence of Oxygen in Earth's Atmosphere Is Thought to Result