單項(xiàng)選擇題

Cooling enables the engine metals （） their mechanical properties.

A.to retain
B.to remain
C.to maintenance
D.to have

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單項(xiàng)選擇題

Constant cooling the various components of diesel engine has a number of functions except for （）.

A.good lubrication
B.low thermal stress
C.good mechanical properties
D.acid corrosion

單項(xiàng)選擇題

Compressed air is used on board ship （）.

A.for starting diesel engines
B.in pneumatic control system
C.in pneumatic tools
D.All the above are true