What type of fire extinguisher is recommended for flammable gas fires?

Flammable gas fires involve combustible materials that can readily ignite and burn. A Class B fire extinguisher is specifically designed for fires involving flammable liquids and gases, such as gasoline, oil, and propane. These extinguishers typically use materials like foam, carbon dioxide, or dry chemicals to effectively smother the flames and prevent the fire from spreading.

Class A extinguishers are suitable for ordinary combustibles such as wood, paper, and cloth but are not effective against gas fires. Class C extinguishers are intended for electrical fires, and Class D extinguishers are used for combustible metals. Therefore, the Class B fire extinguisher stands out as the appropriate choice for extinguishing flammable gas fires, making it the correct answer.