问题：
[单选] For an ordinary four-stroke engine the exhaust valves open （）.
after TDC。before TDC。after BDC。before BDC。
问题：
[单选] For an ordinary four-stroke engine the inlet valves open （）
after TDC。before TDC。after BDC。before BDC。
问题：
[单选] For an ordinary modem marine four-stroke engine the inlet valves close （）.
after TDC。before TDC。after BDC。before BDC。
问题：
[单选] For one or two types of engine, the piston and rod can be withdrawn downwards from the cylinder into the crankcase and then out through the （）.
cylinder casing。cylinder bore。crankcase door。aperture in the cylinder block。
问题：
[单选] For one or two types of engine,the piston and rod can be withdrawn downwards from the cylinder into the crankcase and then out through （）.
the cylinder cover。the bottom of bed-plate。the sump。the crankcase door。
问题：
[单选] Four strokes consist of suction, compression, （） and exhaust stroke.
combustion。condensation。charging。evaporatio。
问题：
[单选] Fresh water is used for the cooling of cylinder jackets and （） of the marine diesel engine.
cylinder covers。lubricating space。crosshead。exhaust manifold。
问题：
[单选] Fuel injection uses the jet pump system and a Woodward type hydraulic （） is used to control engine speed.
controller。governor。instrument。apparatu。
问题：
[单选] Fuel injection valves should be taken out, cleaned, and lifting checked every （）.
two to four months。four to six months。six to eight month。
问题：
[单选] Fuel is delivered into the combustion space by （）.
a cooling system。a lubricating system。an electric system。an injection system。
