Final answer:
Class B fires refer to those involving flammable liquids and gases, common in fuel combustion, waste combustion, and industrial processes.
Step-by-step explanation:
Class B fires involve flammable or combustible liquids and gases such as gasoline, kerosene, grease, and natural gas. These types of fires result from fuel combustion (especially in vehicles), industrial processes that involve flammable liquids or gases, uncontrolled waste combustion, and residential situations such as a kitchen fire involving oils or grease. These fires cannot be extinguished with water because water can spread the flammable liquid, making the fire worse. Instead, they require the use of a Class B fire extinguisher, which typically contains dry chemical agents that smother the fire by cutting off the oxygen supply or by halting the chemical reaction at the fire's source.