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.inside the bearing
B.outside the bearing
C.covering the crankshaft
D.none of the above

A.seized
B.clogged
C.melted
D.inserted

A.sufficient quantity； measured
B.measured quantity；sufficient
C.excessive quantity；sufficient
D.the less quantity the better；the more the better