Refer to the exhibit. Router 1 is missing the route for the router 2 loopback 0. What should the engineer change to fix the problem?

OSPF routers must be configured with identical area numbers when they are intended to be in the same OSPF area; differing area numbers will prevent them from forming a full adjacency and exchanging routes directly within that area.

An incorrect wildcard mask in Router 2's OSPF `network` statement might prevent its loopback from being advertised, but it wouldn't be the primary reason for Router 1 missing the route if adjacencies aren't forming due to area mismatch.

Router 1 becoming an ABR (Area Border Router) is relevant if R1 and R2 are in *different* areas and need to exchange inter-area routes, which is a different scenario from missing a directly connected loopback route in the same area.

OSPF hello timers must be *identical* between neighbors for an adjacency to form; making them different would break, not fix, neighbor relationships.