单项选择题

The sealing function of the piston ring is brought about by the gas pressure above and behind the piston ring, which forces it （） against the bottom of the ring groove, and （） against the cylinder wall.

A.upwards；inwards
B.upwards；outwards
C.downwards；inwards
D.downwards；outwards

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单项选择题

The scavenge port inspection should be carried out（）, to obtain the most reliable result with regard to the effectiveness and sufficiency of the cylinder lubrication and the combustion cycle (complete or incomplete).

A.at the first stop after a long voyage egby anchoring if possible
B.at the first stop after arrival at harbor
C.at the first stop after low load running
D.at the first stop after passing river or canal passage

单项选择题

Always ensure that the turning gear is（）, even at the quay, the wake from other ships may turn the propeller and thus the engine.

A.disengaged
B.engaged
C.assembled
D.disassembled

单项选择题

In general, the oil mist defectors include a base plate with air blast pumpThe function of air blast pump is to （）crankcase.

A.supply clean air to the measuring compartment of the units for more accuracy
B.generaate the pressure required for the extraction of the oil mist from the
C.generate the pressure required for the extraction of the oil mist from the crankcase
D.supply clean air to the measuring track of the units for more accuracy