Understanding the cultural habits of another nation,especially ______containing as many different subcultures as the United States,is a complex task.

A．one

B．the one

C．that

D．such

操作过电压大小以（）峰值的倍数来表示。

A.最高工作相电压；

B.线电压；

C.相电压；

D.最高工作线电压。