Two OSPF neighbors exchange Hellos but never form adjacency. Router A is configured for MD5 authentication on the interface; Router B is configured with no authentication. What behavior will you observe?

OSPF neighbors must agree on authentication type and credentials to form an adjacency. In this scenario, Router A expects MD5 authentication, while Router B sends Hellos without any authentication. This mismatch prevents the routers from transitioning beyond the Init state, as they cannot successfully authenticate each other's Hello packets. Therefore, they will not form an adjacency or exchange LSAs. The other options are incorrect because OSPF authentication mismatches always prevent adjacency formation; they do not lead to partial adjacency, passive mode operation, or conditional adjacency based on area configuration.