正解:C
In a Cisco Wireless LAN Controller (WLC) setup, the controller management interface is used as the source for all RADIUS-related traffic when the interfaces are not in the same subnet as the RADIUS server. This interface is specifically designated for in-band management of the device, system traffic, and RADIUS-related communication, ensuring secure and reliable authentication and authorization services. References
:= Implementing and Operating Cisco Service Provider Network Core Technologies