单项选择题
Large marine diesel engines of crosshead construction generally have two systems of lubrication: a total loss system feeding the （） and a recirculation system lubricating the running gear and cooling the piston.
A.cylinder liners and piston rings B.main bearings C.crankpin bearings D.turboblower
单项选择题 Keep compartment （） as the gas given off can be dangerous.
单项选择题 It is well known that good lubrication will （） the bearings from becoming overheated.
单项选择题 It is very necessary that each cylinder （） before the charged air is compressed.
