Multiple choice

_____________ is not ideally a constituent of air.

  1. Oxygen

  2. Nitrogen

  3. Carbon monoxide

  4. Water vapour

  5. Carbon dioxide
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This is the correct option. Carbon monoxide (CO) is a colourless, odourless and tasteless gas that is slightly less dense than air. It is toxic to humans and animals. 

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