Which class of fire should be tackled using water?

Water is effective for extinguishing Class A fires, which typically involve ordinary combustible materials such as wood, paper, cloth, rubber, and some plastics. These materials can absorb water, which helps in cooling them down and extinguishing the flames. When water is applied, it reduces the temperature below the ignition point and helps to suppress the fire effectively.

Class B fires involve flammable liquids and gases, and using water on these types of fires can be dangerous, as it may spread the fire or create additional hazards. Class C fires involve live electrical equipment, where using water could lead to electrocution or further damage to electrical systems. Class D fires involve combustible metals; these require specific agents that can smother or chemically react with the burning materials, and water is typically ineffective in those situations.

Therefore, using water is appropriate and safe only for Class A fires, making it the correct answer to this question.