Approximately how long after the Solar System formed did it take for oxygen to get to within 80 percent of its present abundance in Earth's atmosphere?
A) 4 billion years
B) 1 billion years
C) 400 million years
D) 1 million years
E) Oxygen was always a primary component of Earth's atmosphere.

Question

Quizplus · Accepted Answer

It took approximately 4 billion years for oxygen to reach 80 percent of its present abundance in Earth's atmosphere, primarily due to the gradual process of photosynthesis by cyanobacteria and other photosynthetic organisms.

Approximately How Long After the Solar System Formed Did It