单项选择题
The crown is fairly thick with the cylindrical parts （） to a thinner section.
A.forged B.tapering C.drilling D.boring
单项选择题 The cross-head shoes are white metal lined, grooves being cut horizontally on the face of the white metal to ensure （）.
单项选择题 The cross-head shoes are white metal （）.
单项选择题 The crankshafts of medium speed engines are almost invariably solid （） from a single piece of steel.
