OSPF routing uses the concept of areas. What are the characteristics of OSPF areas? ()
A、A.Each OSPF area requires a loopback interface to be configured.
B、B.Areas may be assigned any number from 0 to 65535.
C、C.Area 0 is called the backbone area.
D、D.Hierarchical OSPF networks do not require multiple areas.
E、E.Multiple OSPF areas must connect to area 0.
F、F.Single area OSPF networks must be configured in area 1.