通常，根据所传递的内容不同，可将系统总线分为3类：数据总线、地址总线和（）。
A、I/O总线
B、控制总线
C、系统总线
D、内部总线
参考答案：B
已知圆C：x2+y2-4y=0，过点（3，2）作圆的切线，则切线长等于______．
句型转换
1. Millie gives me some candy. (改为一般疑问句)
Millie give you candy？
2. There is only one packet of salt in the kitchen. (对划线部分提问)
packets of salt are there in the kitchen?
3. We often watch one hour of TV every evening. (保持句意基本不变)
We often TV one hour every evening.
4. Do you study at weekends?(将时间状语替换为at present)
you at present?
5. Each student can spend $5. (保持句意基本不变)
The each student is $5.
