單項(xiàng)選擇題

The conclusion that mechanical efficiency is always （） 100 percent is correct.

A.small than
B.more than
C.little than
D.less than

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單項(xiàng)選擇題

The compressed air is supplied by （） to the air reservoirs.

A.compressors
B.forced fans
C.ventilators
D.generators

單項(xiàng)選擇題

The compressed air is admitted to each cylinder through a cam operated by starting air valve when the piston has just passed its （）.

A.BDC
B.TDC
C.BBDC
D.ATDC