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单选题
For an ordinary four-stroke diesel engine the exhaust valves close （）.
A
after TDC
B
before TDC
C
after BDC
D
before BDC
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单选题The size of the exhaust valve opening is （）A
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单选题The loss of the diesel engine cylinder air charge through leaky valves, piston rings, worn or scored liners, would be indicated by which of the following sets of conditions?（）A
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