How did oxygen (O2) get into Earth's atmosphere?
A. It was captured from the solar nebula.
B. It was outgassed from volcanoes.
C. It came from chemical reactions with surface rocks.
D. It was released by life through the process of photosynthesis.
Answer:D
How did oxygen (O2) get into Earth's atmosphere?
A. It was captured from the solar nebula. B. It was outgassed from volcanoes. C. It came from chemical reactions with surface rocks. D. It was released by life through the process of photosynthesis.