1. [单选题]关于帧中继的说法，正确的是（）
A. 速率最大为1Mbit/s
B. 不提供差错校验功能
C. 可以偷占带宽
D. 数据传输质量高于DDN
2. [单选题]The Ezonexam network administrator has issued the "VTP password ezonexam" command on a Cisco device. What is the purpose of this command?
A. It allows two VTP servers to exists in the same domain, each configured with different passwords
B. It is the password required when promoting a switch from VTP client mode to VTP server mode
C. It is used to access the VTP server to make changes to the VTP configuration
D. It is used to validate the sources of VTP advertisements sent between switches
E. None of the above
3. [单选题]OSI七层模型中，“段”是哪一层数据封装的名称（）
A. 物理层
B. 数据链路层(data link layer)
C. 网络层
D. 传输层
