Which two implementations are standard Virtual Private LAN Service （VPLS） implementations that aresupported by the IETF？（）

• A、VPLS uses LDP for signaling.
• B、VPLS uses BGP for autodiscovery and signaling.
• C、VPLS uses extended IS-IS for signaling
• D、VPLS uses OSPF version 3 for auto discovery and signaling
• E、VPLS uses spanning tree for signaling