Which class of fire involves ordinary combustibles, such as wood, paper, cloth, rubber, and some plastics?

The correct choice pertains to Class A fires, which specifically involve ordinary combustibles. This class is characterized by materials that are found in everyday items, including wood, paper, cloth, rubber, and certain plastics. Fires of this nature can be extinguished using water, foam, or dry chemical extinguishers designed for Class A materials.

In understanding Class A fires, it is essential to recognize that these are typically the most common types encountered in residential and commercial settings, making knowledge of their characteristics important for firefighting. Water is effective in cooling the burning materials and ultimately extinguishing the fire.

The other fire classes, such as B and C, classify fires based on different types of combustible materials, like flammable liquids and gases. Thus, recognizing the specific characteristics of each class of fire helps firefighters effectively choose the correct extinguishing agents and methods.