Which of the following is NOT a classification of fire extinguishers?

Fire extinguishers are classified based on the types of fires they are designed to combat. Each class corresponds to specific materials that are burning. The classifications are as follows:

• Class A extinguishers are used for ordinary combustibles such as wood, paper, and cloth.

• Class B extinguishers are intended for flammable liquids, including gasoline, oil, and paint.

• Class C extinguishers are designed for electrical fires that involve energized electrical equipment.

• Class D extinguishers are specific to fires involving combustible metals, such as magnesium, titanium, and sodium.

In this context, the classification D refers to a legitimate category of fire extinguishers, specifically for combustible metals. Therefore, the correct answer indicates that it does not represent an incorrect classification. Options A, B, and C are all established classifications of fire extinguishers used for various types of fires, which reinforces that D is recognized as a valid category. Thus, there is no non-classification among the given options.