单项选择题 After issuing the "show version" command on your Cisco router, you notice that the image is named "C7200-ajs40-mx". What does the C7200 portion of the filename represent?（）

单项选择题 You need to upgrade the IOS of an existing router on your network. The new IOS image is located on a TFTP server that you have set up within the network. What command should you issue in order to download the new IOS version?（）

单项选择题 After making changes to the router, you issue the "copy running-config startup-config" command to save changes. After reloading the router, the router comes up in setup mode. You again make changes, save them, and reboot. Again,the router comes up in setup mode. What is the most likely cause of this?（）