Multiple choice

What gas makes up 78% of the air?

  1. Nitrogen

  2. Oxygen

  3. Carbon dioxide

  4. Water

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

Nitrogen is the most abundant gas in Earth's atmosphere, making up approximately 78% of dry air. Oxygen is the second most abundant at about 21%, while carbon dioxide and water vapor exist in much smaller amounts.