Refer to the exhibit. Why does the OSPF neighborship fail between the two interfaces?

While an MTU mismatch can cause OSPF neighborship issues (stuck in EXSTART/EXCHANGE), it typically manifests after the initial IP connectivity check, and is not as fundamental as a subnet mismatch.

Different OSPF timers (Hello/Dead) can prevent neighborship from forming or cause it to drop, but usually only after initial communication, and it's a separate check from the fundamental IP subnet match.

An OSPF interface network type mismatch (e.g., point-to-point vs. broadcast) can cause issues, but a subnet mismatch is a more direct and fundamental layer 3 connectivity problem that precedes network type considerations.

For OSPF routers to establish a neighborship, they must be on the same IP subnet. If the IP subnet masks configured on the interfaces are different, even if the IP addresses appear to be in the same range, the routers will not recognize each other as being in the same broadcast domain, which is a fundamental requirement for OSPF adjacency formation.