Refer to the exhibit. Which configuration prevents the OSPF neighbor from establishing?

OSPF includes the interface MTU value in its Database Descriptor (DBD) packets. If the MTU values on connected interfaces do not match, OSPF adjacency will not establish, as the routers interpret it as a potential fragmentation issue or protocol mismatch.

Duplex mismatch can cause performance issues and packet loss but typically does not prevent OSPF adjacency establishment directly.

An incorrect network statement might prevent an interface from participating in OSPF, but it doesn't directly prevent adjacency *establishment* if two interfaces are otherwise correctly configured and exchange Hellos.

The default-metric configuration affects how external routes are imported into OSPF and does not impact the adjacency formation process between neighbors.