Which two conditions can prevent OSPF routers from forming an adjacency?

Mismatched hello and dead timers prevent OSPF routers from forming an adjacency because OSPF requires these timers to be identical on directly connected interfaces to ensure consistent neighbor discovery and maintenance. If they don't match, routers will not recognize each other as valid neighbors. The use of the same router ID on both devices is also a critical issue. OSPF router IDs must be unique within an OSPF domain to identify each router distinctly. Duplicate router IDs cause conflicts and prevent proper adjacency formation, as routers cannot differentiate between themselves and another device. Mismatched autonomous system numbers are not relevant to OSPF adjacency, as OSPF uses process IDs, not ASNs. An ACL blocking traffic from multicast address 224.0.0.10 would prevent adjacency, but this option specifies 224.0.0.10, which is the EIGRP multicast address, not OSPF's 224.0.0.5 or 224.0.0.6. Mismatched process IDs do not prevent adjacency; they simply define different OSPF processes on a router, which can still form adjacencies with routers in the same process.