All portable extinguishers are rated according to their:

• A. Size
• B. Intended use
• C. Cooling potential
• D. Conductivity

Answer: (B)

Extinguishing equipment is rated by the class of fire it’s intended to handle. This rating tells you the specific fire hazards the extinguisher is designed to fight (for example ordinary combustibles, flammable liquids, electrical equipment, metals, cooking fires). That intended-use information is what you rely on to choose the right extinguisher for a given situation. The rating isn’t about the extinguisher’s size, nor about how much cooling it provides, nor about conductivity. Those factors may affect performance, but the official rating is about which fire hazards it’s suitable for.