At the end of which of the following periods did oxygen concentrations decrease from about 30 percent to 15 percent?

Question

Quizplus · Accepted Answer

The decrease in oxygen concentrations from about 30 percent to 15 percent occurred at the end of the Permian period, which is also known as the Permian-Triassic extinction event. This event resulted in the loss of approximately 90 percent of marine species and 70 percent of terrestrial species, making it the most severe mass extinction event in Earth's history.

At the End of Which of the Following Periods Did