Which of the following are true statements regarding the characteristics of OSPF areas? Select all that apply.（）

A、AllOSPFnetworksrequiretheuseofmultipleareas
B、MultipleOSPFareasmustconnecttoarea0
C、SingleareaOSPFnetworksmustbeconfiguredinarea1
D、Areascanbeassignedanynumberfrom0to63535
E、Area0iscalledthebackbonearea
F、EachOSPFareaneedtobeconfiguredwithaloopbackinterface