What does the term head mean when applied to a fire pump?（）

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?（）

A.Smothers burning surfaces，organically destroys fuel
B.Cools fire and adjacent surfaces，provides protective barrier
C.Reaches areas not protected by steam or CO₂ smothering systems
D.Allows fire to be attacked from leeward，saturates liquid surfaces

单项选择题Weight is considered during the periodic required inspection and servicing of（）.

A.CO₂ (carbon dioxide) fire extinguishers
B.foam fire extinguishers
C.water (stored pressure) fire extinguishers
D.All of the above

单项选择题Water fog from an all-purpose nozzle may be used to（）.

A.fight an electrical fire
B.fight a magnesium fire
C.eliminate smoke from a compartment
D.All of the above

单项选择题Ventilation systems connected to a compartment in which a fire is burning are normally closed to prevent the rapid spread of the fire by（）.

A.convection
B.conduction
C.radiation
D.spontaneous combustion