Which of the following is the best fire extinguisher?

Correct answer: (d) Carbon dioxide

Explanation

Carbon dioxide is a very good fire extinguisher: it is heavier than air, so it settles over the fire and cuts off the oxygen, and it does not burn or conduct electricity.

That makes CO₂ extinguishers safe for electrical and oil fires, where water can be dangerous. Oxygen makes a fire burn more fiercely.