Refer to the exhibit. Why are routers R1 and R2 not exchanging OSPF routers?
R1(config)# router ospf 2 R1(config)# network 10.10.10.0 0.0.0.255 area 1 R1(config)# network 20.20.20.0 0.0.0.255 area 2 R1(config)# router-id 15.15.15.15
R2(config)# router ospf 10 R2(config)# network 10.10.10.0 0.0.0.255 area 1 R2(config)# network 20.20.20.0 0.0.0.255 area 2 R2(config)# router-id 16.16.16.16

A.	The OSPF process numbers are different.
B.	There is no backbone area configured.
C.	The router IDs are different.
D.	OSPF is not enabled on the interfaces.