To extinguish a Class C fire, which of the following is most appropriate?

To effectively extinguish a Class C fire, which involves energized electrical equipment, the use of a dry chemical extinguisher labeled ABC is the most appropriate choice. Dry chemical extinguishers work by discharging a powder that interrupts the chemical reaction that fuels the fire. They are safe to use on live electrical equipment because they do not conduct electricity, thereby minimizing the risk of electric shock to the operator.

Using water on a Class C fire can be dangerous, as water is a conductor of electricity and may cause electric shock or further complicate the fire. Foam and wet chemical extinguishers are typically used for Class A and B fires; foam is effective on flammable liquids, while wet chemical extinguishers are designed mainly for cooking oils and fats. Therefore, the best choice to extinguish a Class C fire is indeed a dry chemical ABC extinguisher, ensuring both safety and effectiveness.