A.has left
B.had left
C.has been away
D.had been away
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A.in
B.to
C.from
D.by
A.stand by
B.stand for
C.stood by
D.stood for
A.to pay attention
B.paying attention
C.pay attention
D.your paying attention
A.operated
B.made
C.run
D.done
A.which
B.what
C.that
D.whose
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（）are used to digest the sewage to produce innocuous sludge in a biological sewage treatment plant.
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The shipboard oil pollution emergency plan will be invalid after （）
（） is not installed on the main switchboar.
The main purpose of port State control is not to（）
The treatment of the fuel oils involves storage, heating, filtering and（）
By comparing the exhaust gas temperature of each cylinder, the operator can determine if the load is balanced throughout the engine. The device most commonly used is a（）
Which of the diesel engine components listed increase air density and helps to improve engine operating efficiency?（）
Which of the listed governor characteristics will greatly affect the load sharing relationship between paralleled diesel generators?（）
The condensers located in various stages of a flash evaporator are cooled by（）