问题
单项选择题
Communication networks can be classified in terms of their physical arrangement or (74) Three common (74) are the star, bus, and ting.
A．structures
B．topologies
C．protocols
D．frames
答案
参考答案：B
解析：[分析] 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形、总线型和环形。