Customer X has a hub-and-spoke Frame Relay network， with a central office and two branch offices （RemoteA and RemoteB）. Each location has only one physical link to the Frame Relay cloud and RemoteB has a router that is not a Cisco router. Since the installation， there is no connectivity between RemoteB and the central office. What is a possible solution to this issue？ （）

A、 Because Frame Relay IETF encapsulation is only configurable at interface level， you must use IETF encapsulation on all routers.

B、 This is not a possible scenario. A dedicated Frame Relay link to RemoteB is mandatory at the central office.

C、 The router at RemoteB must be replaced by a Cisco router.

D、 Use Frame Relay IETF encapsulation on a per-VC basis on the central office router.

E、 There is a problem in the Frame Relay cloud， because Cisco routers are compatible with IETF Frame Relay.