There are many places in the world ________ have been visited only by a few, many ________ are

of an enormous beauty.[      ]

A. where; of which  

B. which; of whom

C. that; of which  

D. that; of whom

在进行热熔连接操作时，清洁加热板其表面聚乙烯的残留物只能用（）工具去除。

A、铁质

B、钢质

C、铜质

D、木质