Which two of the following are considered valid router IDs for EIGRPv6？ （）

A.excessive collisions
B.FCS errors
C.runts
D.late collisions

A.BPDUs that enter a blocking port are discarded.
B.BPDUs that enter a blocking port are processed.
C.Loopguard puts an interface into a loop-inconsistent state when BPDUs stop being received on a blocking port.
D.BPDUs are only processed on forwarding ports.