单项选择题
What does blowing tubes accomplish?（）
A.Eliminates unburned fuel oil residues from the firebox B.Increases boiler efficiency C.Flushes away mineral deposits inside the water tubes D.Cleans soot deposits from the inside of the stack
单项选择题 What are the most important reasons for using water fog to fight fires?（）
单项选择题 Weight is considered during the periodic required inspection and servicing of（）.
单项选择题 Water fog from an all-purpose nozzle may be used to（）.
