The gaseous oxygen in Earth's atmosphere was produced as a by-product of which process?
A)Volcanic outgassing.
B)Photochemical reactions breaking down ozone (O3)to form oxygen (O2).
C)Photosynthesis.
D)Decay of organic matter.

Question

Quizplus · Accepted Answer

The gaseous oxygen in Earth's atmosphere was produced as a by-product of photosynthesis, which is the process by which plants, algae, and some bacteria use sunlight and carbon dioxide to produce organic compounds and oxygen. This process started about 3 billion years ago and gradually led to the buildup of oxygen in the atmosphere, which allowed for the evolution of aerobic organisms. Volcanic outgassing, photochemical reactions breaking down ozone, and decay of organic matter all contribute to the chemical composition of the atmosphere, but they did not produce the significant amount of oxygen that is present today.

The Gaseous Oxygen in Earth's Atmosphere Was Produced as a By-Product