A:A,B是导体,C,D是绝缘体
B:C,D是导体,A,B是绝缘体
C:A,D是导体,B,C是绝缘体
D:A,B,C,D都是导体
已知m﹣n=2,mn=﹣1,则(1+2m)(1﹣2n)的值为( )
We all know that it is very important for us to learn ____ (口语的) English.