单项选择题
A.a coil spring B.a sealing ring C.an oil distributor ring D.main seal ring
The lower end of each piston rod is reduced in diameter...
单项选择题The lower end of each piston rod is reduced in diameter to fit a bore in （）.
A.the crosshead B.the journals of the crosshead C.the crosshead shoes D.the guides
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.
A.the crank-web B.the connecting rod C.the main bearing D.the cross-head
单项选择题The lower end of each piston rod is reduced in diameter to fit a bore in the cross-head, this being secured to the piston rod by （）.
A.a bolt B.a cap C.a disc D.a nut
