Question

Which describes oxygen content as Earth evolved over time? Oxygen levels sharply declined about 400 million years ago. Oxygen levels stay above 15 percent starting 200 million years ago Oxygen levels remain below 5 percent starting 1000 million years ago. Oxygen levels raise significantly between 1000 and 700 million years ago.

Answer 1

b

Step-by-step explanation:

Answer 2

Oxygen levels stay above 15 percent starting 200 million years ago

Step-by-step explanation:

Atmospheric oxygen levels are related to the evolution on Earth and changes in geochemical cycles that involve climate variations.

The presence of O 2 and evolution of oxygen gave new opportunities to the life on Earth. Oxygen levels in atmosphere have fluctuated between 15% and 35% of atmospheric volume, since the start of the Cambrian period.

So, form the starting 200 million years ago, oxygen level stay above 15 percent and the correct option is "B".