单项选择题
A.The compressed air B.The compressing air C.The transfer pump D.The head tank
Under rotary pumps are the gear, （）, cam-and-piston and...
单项选择题Under rotary pumps are the gear, （）, cam-and-piston and screw types.
A.reciprocating B.diffuser C.turbine D.vane
The water level in the gauge glass when a boiler is ope...
单项选择题The water level in the gauge glass when a boiler is operating is （） when the boiler is shut down.
A.lower than B.higher than C.below D.equal to
Large pipes or （） are fitted between the steam and wate...
单项选择题Large pipes or （） are fitted between the steam and water drums to ensure good natural circulation of water.
A.fire-tubes B.furnaces C.down-comers D.soot-blowers
