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KATRIN_1 [288]
3 years ago
8

Which describes oxygen content as Earth evolved over time? Oxygen levels sharply declined about 400 million years ago. Oxygen le

vels 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.
Biology
2 answers:
lora16 [44]3 years ago
5 0

Answer:

b

Explanation:

tankabanditka [31]3 years ago
4 0

the correct answer is b. i just took the quiz

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