单项选择题
The main bearing shells are made of steel with a lining of bearing metal which may be white metal, copper-lead or aluminum-tin alloy What is the meaning of “which” in the sentence above?（）
A.main bearing shells B.main bearing C.steel D.bearing metal
单项选择题 The main bearing metal is a lining （）.
单项选择题 The machine has stopped rotating because the bearing （） the shaft.
单项选择题 The lubricating system for the cylinder walls is different from the bearings in that the oil for former one is supplied in （） while that for latter one is （）.
