活动圈主题编号由（）编写
A.公司工作组
B.厂处工作组
C.辅导员
D.圈长
参考答案：B
— ____ the Internet ____ in your school?
— Yes, but the computer in our office has often broken down. [ ]
A. Is, used
B. Is, using
C. Does, use
D. Has, used
交流电变化一个循环所需的时间叫做交流电的频率。（）
