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