Multiple choice

Which of the following is a poisonous gas?

  1. Hydrogen

  2. Oxygen

  3. Carbon dioxide

  4. Mustard gas

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

Mustard gas is a poisonous chemical warfare agent that causes severe burns and respiratory damage. Hydrogen and oxygen are essential elements for life, while carbon dioxide is a natural byproduct of respiration that is not poisonous at normal concentrations.