—What would you wish to do if you were a college student again?

—That's very hard to say, but I wish I when I was a college student.

A．has not studied biology

B．did study biology

C．had studied biology

D．studied biology

以下哪种可作为电缆绝缘层的材料（）。

A.聚氯乙烯

B.聚乙烯

C.交联聚乙烯

D.油浸纸