单项选择题
A.after TDC B.before TDC C.after BDC D.before BDC
For an ordinary four-stroke engine the exhaust valves o...
单项选择题For an ordinary four-stroke engine the exhaust valves open （）.
For an ordinary four-stroke diesel engine the exhaust v...
单项选择题For an ordinary four-stroke diesel engine the exhaust valves close （）.
For a main diesel engine the lube oil in the bearings i...
单项选择题For a main diesel engine the lube oil in the bearings is drawn from （）, usually located in the bedplate.
A.a gravity tank B.a sump C.a vessel D.a bottle
