According to the figure shown below, approximately how many years ago did oxygen finally get to half its current abundance in Earth's atmosphere?

Question

Quizplus · Accepted Answer

The figure shows that it took approximately 2 billion years for oxygen to reach half its current abundance in Earth's atmosphere. Since the present day is approximately 2.5 billion years after the Great Oxygenation Event, we can subtract 2 billion from 2.5 billion to get 0.5 billion, which is the approximate time when oxygen reached half its current abundance. Therefore, the answer is C, 0.6 billion years ago (which is the closest choice).

According to the Figure Shown Below, Approximately How Many Years