Multiple choice

The percentage of oxygen in the atmosphere is

  1. 7.8%

  2. 0.03 to 0.04%

  3. 21%

  4. 2.45%
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The percentage of oxygen in the atmosphere is 21%. The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. Even if the atmosphere today has only 21 percent oxygen, today is still regarded as a period with rapid development of animals because of a high amount of oxygen in the atmosphere. 

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