单项选择题
Firefighting foam is only effective when the foam（）.
A.penetrates to the bottom of the fire B.is kept saturated with low-velocity water fog C.mixes with the burning fuel oil D.completely covers the top of the burning liquid
单项选择题 Fire may be spread by which means?（）.
单项选择题 Fire in an engine compartment is best extinguished with carbon dioxide gas (CO2) and by（）.
单项选择题 Fire hose should be washed with（）.
