What are two reasons that will prevent two routers from forming an OSPFv2 adjacency? (Choose two.)
mismatched subnet masks on the link interfaces
a mismatched Cisco IOS version that is used
mismatched OSPF Hello or Dead timers
use of private IP addresses on the link interfaces
one router connecting to a FastEthernet port on the switch and the other connecting to a GigabitEthernet port