單項(xiàng)選擇題The is employed to warm up a large diesel engine before its starting（）

A.hot air
B.hot boiler water
C.cylinder water
D.hot seawater


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1.單項(xiàng)選擇題In slow speed two-stroke engines,（）the fresh air entering begins when and stops as（）

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

2.單項(xiàng)選擇題Usually we take the cooling effect of the air flown through the cylinder during the overlap period as（）

A.inevitable
B.harmful
C.helpful
D.unacceptable

3.單項(xiàng)選擇題When the air charge contacts with the cylinders and pistons and mixes with the residual gases, it will（）

A.increase in temperature
B.lose its energy partly
C.expand and do work
D.begin to be compressed

5.單項(xiàng)選擇題Gas exchange, which is a basic part of the cycle of an internal combustion engine, is（）

A.the supply of normal air and removal of compressed air
B.the supply of fuel oil and combustion of the atomized oil
C.the supply of fresh air and removal of exhaust gases
D.the supply of fresh air and removal of the extra heat