What risk does Class B foam primarily address?

Class B foam is specifically designed to combat flammable liquid fires, making it the most suitable choice. The effectiveness of Class B foam stems from its ability to create a barrier between the burning liquid and the environment, which helps to suppress flames and prevent re-ignition. This foam works by smothering the fire, cooling the surface, and preventing vapors from escaping, which is crucial for managing fires involving substances such as gasoline, oil, and other hydrocarbons.

In contrast, options like electrical fires, solid waste fires, and aerosol fires do not primarily involve flammable liquids as their main component. While certain foams can assist in various fire suppression scenarios, Class B foam's unique formulation is particularly suited to address the challenges posed by flammable liquids, making it the best answer to the question.