Class B foam fire extinguishers are also effective on:

Class B foam fire extinguishers are specifically designed to combat flammable liquid fires, which classifies them as suitable for Class B fires. However, they can also be effective on Class A fires, which involve ordinary combustibles such as wood, paper, and some textiles.

When foam is deployed on a Class A fire, it creates a blanket over the burning materials, smothering the fire and preventing oxygen from reaching the fuel. The cooling effect of the foam can also help to extinguish the flames. This versatility makes Class B foam effective for both Class B and Class A fires, thus providing an additional layer of safety in various firefighting scenarios.

In contrast, while Class C fires involve electrical equipment, the use of foam can create risks due to its conductive properties and potential for equipment damage. Cooking oil fires are better addressed using specific fire extinguishers designed for greases and oils, such as Class K extinguishers, given that cooking oils can burn at higher temperatures than typical Class A materials. Therefore, Class B foam is not ideal for those applications. The option stating "None of these is correct" does not apply because Class A fires can indeed be effectively managed with Class B foam extinguishers.