用500型指针式万用表测量（）时，每更换一次量程都必须调零。
A.电压
B.电流
C.电阻
D.电容
参考答案：C
I suggested my father that we________to Dalian for a holiday this summer，but the expression
on his face suggested that he________to it.[ ]
A．go；shouldn’t agree
B．would go；shouldn’t agree
C．go；didn’t agree
D．would go；didn’t agree
简述蜂窝移动通信系统中，用来提高抗干扰的几种技术（最少四种）
