唐朝的著名帝王宫苑和郊野别墅有哪些？

A. it is not used in multicast
B. it determines the virtual address group for a multicast destination
C. it dynamically registers individual hosts in a multicast group on a specific LAN
D. it is used on WAN connections to determine the maximum bandwidth of a connection
E. it determines whether Bidirectional PIM or PIM sparse mode will be used for a multicast flow

A. 往返测
B. 单程观测
C. 单程双测站