The modern concentration of 21 percent molecular oxygen in our atmosphere resulted largely from:
A) meteorite impacts.
B) non-biological activity.
C) biologic activity.
D) the big bang theory.

Question

Quizplus · Accepted Answer

The modern concentration of oxygen in our atmosphere is largely the result of biological activity, specifically photosynthesis by plants and other organisms that produces oxygen as a byproduct. Non-biological activities such as geological processes and meteorite impacts may have played a role in the past, but are not the main contributor to the current atmospheric oxygen levels. The big bang theory is not relevant to the concentration of oxygen on Earth.

The Modern Concentration of 21 Percent Molecular Oxygen in Our