Distinguish between class a and b fires?

Class A fires involve ordinary combustible materials such as wood, paper, cloth, and plastics. These fires can be extinguished with water, foam, or dry chemical extinguishers.

Class B fires involve flammable liquids and gases such as gasoline, oil, grease, and propane. These fires can be extinguished with foam, dry chemical, or carbon dioxide extinguishers. Water should not be used to extinguish Class B fires as it can spread the flames and cause the fire to become more intense.