Which two tunneling techniques support IPv6 multicasting？ （）

A.Prepend extra AS hops to the BGP prefix.
B.Advertise more specific BGP prefixes（longer mask）.
C.Add（prepend）one or more communities to the prefix that is advertised by BGP.
D.Have BGP dampen the prefix.

A.the entire network switches to 802.1D and generates BPDUs to determine root bridfe status.
B.A migration delay of three seconds occurs when the port that is connected to the 802.1D bridge comes up
C.The entire network reconverges and a unique root briddge for the 802.1D segment， and a root bridge for the 802.1W segment， is chosen
D.the first hop 802.1w switch that is connected to the 802.1D runs entirely in 802.1DCompatibility mode and converts the BPDUs to either 802.1D or 802.1W segments of the network
E.Classic 802.1D timers， Such as forward Delay and Max-age， will only be used as a backup， and will not be necessary if point-to-point links and edge prots are properly identified and set by the administrator.

A.Out-of-profile packets are queued.
B.It causes TCP retransmits.
C.Marking/remarking is not supported.
D.It does not respond to BECN and ForeSight Messages.
E.It uses a single/two-bucket mechanism for metering.