1. [单选题]IP扩展访问列表的数字标示范围是多少（）。
A. 0-99
B. 1-99
C. 100-199
D. 101-200
2. [单选题]要把交换机的配置文件保存到tftp服务器，应使用的命令为（）
A. copy ios tftp
B. copy running-configt ftp
C. copy flash tftp
D. copy config tftp
3. [单选题]While troubleshooting a connectivity problem on the network, you issue the ping command from your PC command prompt, but the output shows "request times out."At which OSI layer is this problem associated with?
A. The data link layer
B. The application layer
C. The access layer
D. The session layer
E. The network layer
