计算机网络拓扑是通过网中结点与通信线路之间的几何关系表示网络中各实体间的（）。
A、联机关系
B、结构关系
C、主次关系
D、层次关系
参考答案：B
用所给词的适当形式填空。
1. He'll leave on February ______ (two).
2. A man is ______ (slow) than a bike.
3. Buses are slow, men (人) are ______ (slow).
4. I want my mother ______ (buy) me a new bike.
5. May I ______ (invite) my friends to my birthday party?
6. She doesn't ______ (know) your name.
低压进户线绝缘子铁脚接地的接地电阻值应不大于（）Ω。
A.4
B.10
C.20
D.30
