Which of these statements about Earth is true?
A) The oxygen in Earth's atmosphere was created by the evaporation of seawater and its dissociation into hydrogen and oxygen by solar UV light.
B) Earth has always had an oxygen-rich atmosphere, which was one reason that life could develop on Earth.
C) Outgassing by volcanic eruptions converted the carbon dioxide-rich atmosphere into an oxygen-rich atmosphere, thus creating conditions in which life could develop.
D) Life developed in a carbon dioxide-rich atmosphere and then converted it into an oxygen-rich atmosphere.

Question

Quizplus · Accepted Answer

The oxygen in Earth's atmosphere is largely the result of photosynthesis by early life forms. These organisms, over billions of years, converted the carbon dioxide-rich atmosphere into an oxygen-rich one, paving the way for more complex life forms to develop.

Which of These Statements About Earth Is True