单项选择题
A．语法解释比特流的每一部分的意义
B．语法规定用户数据与控制信息的结构与格式
C．语法对事件实现的顺序作了详细地说明
D．语法对协议实现方法作出明确的规定
单项选择题 任意的n阶无向简单图的边数m应满足（）。
单项选择题 ASCII is a 7-bit code used to represent numeric, alphabetic, and special printable characters. It also includes codes for control characters, which are （）.
单项选择题 In most wide area networks, the communication subnet consists of two distinct components：transmission lines and （）.