问题：
[单选] The period of valve overlap is when （）.
the inlet valve is open。the exhaust valve is open。both valves are close。both valves are ope。
问题：
[单选] The period when both inlet valves and exhaust valves are open is referred to as （）.
valve loop。valve uniflow。valve overlap。valve grinding。
问题：
[单选] The pistons are cooled by oil supplied from the forced （） system.
fresh water。sea water。lubrication。fuel oil。
问题：
[单选] The piston moves up and down, thus causing the rotational movement of the（）
crankshaft。connecting rod。cross-head。main beating。
问题：
[单选] The piston moving up and down keeps the crankshaft （）.
to revolve。revolved。revolving。to be revolved。
问题：
[单选] The piston ring grooves for a standard engine are （）
chromium-plate against wear。anti-corrosion treated。white metal lined against wear。flame hardened against wear。
问题：
[单选] The piston rings are manufactured with a diameter （） the bore of the cylinder.
larger than。smaller than。equal to。none of the above。
问题：
[单选] The piston rings if found worn out （） and supplied by shipchandler.
must replace。must to be equipped。has to be repaired。have to be renewed。
问题：
[单选] The piston supporting body is mainly subjected to （） stress.
pushing。centrifugal。stretch。compressive。
问题：
[单选] The plunger in the fuel injector pump, usually operated by a （）, is driven up and down when working.
crankshaft。camshaft。piston rod。rack and pinio。
