Multiple choice

Which of the following gases is the major constituent of air?

  1. nitrogen

  2. carbon dioxide

  3. oxygen

  4. hydrogen

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Nitrogen makes up about 78% of Earth's atmosphere by volume, making it the major constituent. Oxygen is second at about 21%, while carbon dioxide is only about 0.04%. Hydrogen exists in trace amounts only.