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單項(xiàng)選擇題

The period of valve overlap is when （）.

A.the inlet valve is open
B.the exhaust valve is open
C.both valves are close
D.both valves are open

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單項(xiàng)選擇題

The outside diameter of the pipe is （） the diameter of the bore of the piston rod, the result being that an annular space formed between the piston rod and the pipe.

A.less than
B.greater than
C.equal to
D.twice larger than

單項(xiàng)選擇題

The outside diameter of the pipe is （） the diameter of the bore of the piston rod, the result being that an annular space formed between the piston rod and the pipe.

A.less than
B.greater than
C.equal to
D.twice larger than