单项选择题
The lube oil in the bearings is drawn from a （）, usually located in the bedplate.
A.tank B.sump C.vessel D.bottle
单项选择题 The lowest ring of a piston is （）.
单项选择题 The lower end of each piston rod is reduced in diameter to fit a bore in （）.
单项选择题 The lower end of each piston rod is reduced in diameter to fit a bore in （）, this being secured to the piston rod by a nut.
