what would cause router A not to form an adjacency with router B?

Refer to the exhibit.

When running OSPF, what would cause router A not to form an adjacency with router B?

A.
The loopback addresses are on different subnets.

B.
The values of the dead timers on the routers are different.

C.
Route summarization is enabled on both routers.

D.
The process identifier on router A is different than the process identifier on router B.