Refer to the graphic. R1 is unable to establish an OSPF neighbor relationship with R3. What are possible reasons for this problem?（）

• A、All of the routers need to be configured for backbone Area 1.
• B、R1 and R2 are the DR and BDR, so OSPF will not establish neighbor adjacency with R3.
• C、A static route has been configured from R1 to R3 and prevents the neighbor adjacency from being established.
• D、The hello and dead interval timers are not set to the same values on R1 and R3.
• E、EIGRP is also configured on these routers with a lower administrative distance.
• F、R1 and R3 are configured in different areas.