Cooling enables the engine metals （） their mechanical properties.

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

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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

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