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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

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