Select the correct alternative:

Fire extinguishers extinguish the fire by

1. cutting off the supply of air
2. bringing down the temperature of fuel
3. increasing the temperature of the fuel
4. supplying air to the fuel
    

Solution:

Fire extinguishers extinguish the fire by cutting off the supply of air and bringing down the temperature of fuel. 

There are three essential requirements for producing fire. These are fuel, air (to supply oxygen), and heat (to raise the temperature of the fuel beyond the ignition temperature). Fire can be controlled by removing one or more of these requirements. The job of a fire extinguisher is to cut off the supply of air or to bring down the temperature of the fuel, or both.