单项选择题
A.a sea water chest B.a change-over chest C.a buffer tank D.a three-way valve
The switchboards are those in which all the live parts ...
单项选择题The switchboards are those in which all the live parts are installed behind the panels and only the operating handles and instruments are on the front（）
A.open B.open front type C.live front type D.dead front type
Modern centrifuge designs enable continuous over a cons...
单项选择题Modern centrifuge designs enable continuous over a considerable period of timeThis is achieved by which is timed to discharge the sludge at regular intervals（）
A.an injection process B.an ejection process C.a separation process D.a heating process
The oil sump, a light welded design, is mounted on the ...
单项选择题The oil sump, a light welded design, is mounted on the engine block from below and sealed by （）
A.O-ring B.gasket C.washer D.packing
