Multiple choice

Which one of the following pollutes the environment?

  1. Oxygen

  2. Carbon monoxide

  3. Nitrogen

  4. Hydrogen

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

Carbon monoxide is a toxic gas that pollutes the air and is harmful to human health. Oxygen, nitrogen, and hydrogen are natural components of air and are not considered pollutants in their normal atmospheric concentrations.