According to scientific evidence, earth’s earliest atmosphere lacked oxygen. Over time, oxygen was added to the atmosphere.

Which statements explain how this change occurred and how it affected life on earth?

Choose all answers that are correct.

A.
The addition of oxygen to the earth's atmosphere helped make possible the development of eukaryotic organisms, which need oxygen to carry out many of their life processes.

B.
When cyanobacteria evolved, they carried out photosynthesis. Oxygen is a product of photosynthesis. The addition of oxygen to earth’s atmosphere helped make possible the development of eukaryotic organisms, which need oxygen to carry out many of their life processes.

C.
The addition of oxygen to the earth's atmosphere helped make possible the development of prokaryotic organisms, which need oxygen to carry out many of their life processes.

D.
When cyanobacteria evolved, they carried out photosynthesis. Oxygen is needed to carry out photosynthesis.

B.
The cynobacteria were already there without the oxygen, so that rules out A, and a lot of prokaryotes were anaerobic, so that rules out C. Finally, Photosynthesis does not require oxygen. Instead, Oxygen is a waste product of it. Therefore, it cannot be D. So, we are only left with B
Hoped this helped :D

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