Which statement is true about Class B foams designed solely for hydrocarbon fires?

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Class B foams that are designed solely for hydrocarbon fires are formulated to create a stable foam blanket on nonpolar fuels. Polar solvents—like acetone, methanol, or ethanol—interact with the foam differently and tend to break down or dissolve the foam film. This destabilizes the blanket and allows the fuel to continue to burn, so the hydrocarbon-only foam isn’t effective on polar solvent fires. To handle those fires, you need an alcohol-resistant Class B foam or other tactics, since simply mixing with water or using a fixed concentration won’t overcome the foam’s lack of compatibility with polar solvents.