单项选择题
The cylinder and piston must be warmed up （） to a temperature of about 140 degF in standing by engine.
A.repeatedly B.quickly C.gradually D.immediately
单项选择题 The crown is fairly thick with the cylindrical parts （） to a thinner section.
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 （）.
