Multiple choice

What percentage of the atmospheric air consists of oxygen?

  1. 10%

  2. 21%

  3. 52%

  4. 78%
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Earth's atmosphere contains approximately 21% oxygen, which is essential for most life forms and combustion. The remaining 78% is mostly nitrogen, with trace gases making up the final 1%. This 21% figure is a fundamental fact in atmospheric science.

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