An etwork administrator has enabled OSPF across an NBMA network and has issued the command ip ospf network nonbroadcast. Given those facts, which two statements are true?（）

A、Interfaces will automatically detect and build adjacencies with neighbor routers

B、DR and BDR elections will not occur

C、DR and BDR elections will occur

D、The neighbor command is required to build adjacencies

E、All routers must be configured in a fully meshed topology with all other routers