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?（）

• A、The authentication needs to be changed to PAP for both routers.
• B、The serial IP addresses of routers are not on the same subnet.
• C、The username/password combination is incorrectly configured.
• D、The router names are incorrectly configured.