单项选择题
A.the inlet port is opened by the up coming piston； the port is closed by the down going
B.the inlet valve is opened by the down going piston；the inlet valve is closed
C.the inlet port is opened by the down going piston；the port is closed by the up coming
D.the inlet valve is opened
单项选择题 Usually we take the cooling effect of the air flown through the cylinder during the overlap period as（）
单项选择题 When the air charge contacts with the cylinders and pistons and mixes with the residual gases, it will（）
单项选择题 “This increase in charge air density is accomplished on most modern diesel engine types by use of exhaust gas turbo-charging, in which a turbine wheel driven by exhaust from the engine is rigidly coupled to a centrifugal type air compressor” According to this sentence, we can know that increases density（）, drives the compressor directly（）