问题
单项选择题
Communication networks can be classified in terms of their physical arrangement or (73) Three common (73) are the star, bus, and ring.
A．structures
B．topologies
C．protocols
D．frames
答案
参考答案：B
解析： 信息网络可以依据物理结构或拓扑结构进行分类，3个典型的拓扑结构是星型、总线型和环形。