What are possible reasons for this problem?

Refer to the graphic.

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

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.

Explanation:
Explanation/Reference:
This question is to examine the conditions for OSPF to create neighborhood.
So as to make the two routers become neighbors, each router must be matched with the following
items:
1. The area ID and its types;
2. Hello and failure time interval timer;
3. OSPF Password (Optional);