Which of the following gases is used in fire extinguishers? 

CO₂

The correct answer is option 1. \(CO_2\)

Fuel, oxygen, and heat are the three components that start a fire. Fire will put out itself if one of the three elements is removed. Oxygen is the only element that carbon dioxide eliminates. Since CO₂ is heavier than oxygen, it blankets the fire. The fire is controlled because the contact between the fuel and oxygen is broken. So, CO₂ is a gas that is employed in fire extinguishers.