Multiple choice

The two main gases that humans breathe are oxygen and ___________.

  1. Nitrogen

  2. Helium

  3. Hydrogen

  4. Carbon
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Earth's atmosphere is composed of about 78% nitrogen and 21% oxygen, making these the two primary gases we inhale with every breath. Although we only use the oxygen for respiration, nitrogen is the most abundant gas we breathe in and out.

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