The best fire extinguisher for a fire involving greases and oils is?

The best fire extinguisher for a fire involving greases and oils is Class B. Class B extinguishers are specifically designed to extinguish flammable liquids, which include oils, greases, gasoline, and other hydrocarbons. These fires can be particularly dangerous due to the flammable nature of the substances involved and the risk of the fire spreading rapidly.

Class B extinguishers typically use agents such as foam, carbon dioxide, or dry chemicals that work by smothering the fire and interrupting the chemical reactions occurring in the flames. Using a Class B extinguisher on fires involving greases and oils is essential as it effectively prevents re-ignition and minimizes damage.

In contrast, other classes do not effectively target this type of fire. Class A extinguishers are meant for ordinary combustibles like wood and paper, while Class C extinguishers are for electrical fires. Class D extinguishers are specialized for combustible metals and are not relevant to fires involving organic materials like oils and greases. Thus, Class B is the correct choice for handling fires involving these substances.