Which class of fires involves combustible metals like magnesium and aluminum?

The correct choice refers to Class D fires, which specifically involve combustible metals such as magnesium, aluminum, and sodium. These types of fires are distinct from others because they require special extinguishing agents that are designed to deal with the unique properties of burning metals. Common extinguishing agents for Class D fires include dry powder agents, which can smother the fire and prevent oxygen from reaching the burning material.

Unlike other classes of fires, Class D fires do not respond well to water or conventional fire extinguishing methods, as water can react violently with certain metals and exacerbate the fire. Understanding the category of a fire is crucial for proper fire containment and safety practices, especially in environments where flammable metals are present.