Refer to the exhibit. Two indirectly connected routers fail to form an OSPF neighborship. What is the cause of the issue?

Failing hello packets would prevent the neighborship from forming beyond the INIT state, which is an earlier stage than the EXSTART/EXCHANGE state often associated with MTU mismatches.

DR/BDR selection dispute could cause issues or delays, but an MTU mismatch directly prevents the DBD exchange necessary for full adjacency, which is a more fundamental problem for two routers trying to become full neighbors.

OSPF includes the interface MTU in its Database Description (DBD) packets. If the MTU values do not match between two OSPF neighbors on a directly connected link, they will fail to form a full adjacency and typically get stuck in the EXSTART/EXCHANGE state, preventing the exchange of routing information.

An OSPF network type mismatch (e.g., point-to-point vs. broadcast) can prevent neighborship formation, but an MTU mismatch is a specific and common cause that often results in the EXSTART/EXCHANGE state.