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單項(xiàng)選擇題

In order to ensure perfect atomization, the fuel oil （） before injection.

A.has to be cooled
B.has heated
C.has preheated
D.has to be preheated

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單項(xiàng)選擇題

In large marine diesel engines cylinder oils usually contain additives formulated to impart the （） to clean the rings and grooves.

A.inefficiency
B.oiliness
C.detergency
D.purity

單項(xiàng)選擇題

In general, （） is suitable for delivering small quantities at high pressure.

A.reciprocating pump
B.gear pump
C.centrifugal pump
D.vane pump

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