单项选择题 While logged into a router you manually shut down the serial 0 interface using the "shutdown" interface configuration command. You then issue the "show interface serial 0" command in exec mode. What could you expect the status of the serial 0 interface to be?（）

单项选择题 There is a connectivity problem between the serial 0/0 interface of router TESTKING1 and the serial 0/0 interface of TESTKING2. A leased line point to point circuit is installed between these two routers. The output from the "show interface serial 0/0" command is displayed below for each of these routers: From your observations of the above exhibit, what is the underlying cause of the problem?（）

单项选择题 The relevant configuration files for the TestKing1 and TestKing2 routers are displayed below: With due consideration to the command outputs, which of the following reasons would you attribute the connectivity problem between the two routers?（）