单项选择题 A high-velocity fog stream can be used in fire fighting situations to drive heat and smoke ahead of the fire fighters in a passageway. This technique should only be used when（）.

单项选择题 A fire hose with a nozzle attached must be connected to each hydrant except when exposed to heavy weather or when the（）.

单项选择题 If you are fighting a fire below the main deck of your vessel，which action is most important concerning the stability of the vessel?（）.