Which type of fire extinguisher uses water-based agents?

The type of fire extinguisher that uses water-based agents is indeed the water type fire extinguisher. Water extinguishers are designed to combat Class A fires, which involve ordinary combustible materials such as wood, paper, cloth, and some plastics. The primary mechanism of a water extinguisher is to cool the burning material and reduce the temperature to a point below its ignition temperature.

When utilizing water-based agents, it is important to remember that they are not suitable for use on fires involving flammable liquids, electrical equipment, or reactive metals, as using water in those situations could exacerbate the fire or create more dangerous conditions.

In contrast, dry chemical extinguishers employ various powders to interrupt the chemical reaction of the fire, foam extinguishers work by smothering fires and preventing oxygen from reaching the fuel, and CO2 extinguishers suffocate the fire by displacing oxygen. None of these options utilize a water-based agent for extinguishing fires, which is what distinguishes the water type fire extinguisher from the others.