What is the correct order of extinguisher classes A, B, C, D?

The correct order of extinguisher classes is based on the types of materials that each class refers to, which is crucial for effective firefighting. Class A extinguishers are designated for ordinary combustibles, such as paper, cloth, and wood. Class B extinguishers are meant for flammable liquids like gasoline, oil, and paint. Class C extinguishers are used for electrical fires, and Class D extinguishers are specifically for combustible metals.

In this context, the sequence that accurately represents the classification is paper (Class A), liquids (Class B), electrical (Class C), and finally metals (Class D). This structure helps in understanding which extinguisher to use based on the type of fire encountered. Thus, the sequence of paper, liquids, electrical, and metal corresponds correctly to the classes of extinguishers.