What happens to routers in an OSPF non-broadcast network type?

In an OSPF (Open Shortest Path First) non-broadcast network type, routers do not automatically discover their neighbors. Therefore, they must be statically configured to define the OSPF neighbors. This is a crucial characteristic of non-broadcast multi-access (NBMA) networks, such as Frame Relay or X.25 networks, where routers are unable to send multicast packets, which are typically used in OSPF to discover neighbors.

In these scenarios, to establish OSPF adjacencies and ensure that routers can communicate effectively, network administrators need to manually specify the neighbors in the OSPF configuration. This static configuration tells each router which adjacent routers to communicate with and allows them to form the necessary OSPF adjacencies to exchange routing information.

The other choices reflect behaviors that are not applicable to non-broadcast networks. For instance, routers in these types of networks do not automatically form adjacencies without prior configuration, nor can they dynamically discover neighbors using techniques such as multicast. Although hello packets are indeed exchanged as part of the OSPF process, they're not sufficient on their own for establishing OSPF relationships without the static configuration that specifies neighbor relationships.