Refer to the exhibit. Which command must be applied to R2 for an OSPF neighborship to form?

The command `network 20.1.1.2 0.0.0.0 area 0` correctly enables OSPF on the interface with IP address 20.1.1.2, assigning it to Area 0. The wildcard mask 0.0.0.0 specifically matches only the host address, making this a valid and precise way to activate OSPF on a single interface.

The wildcard mask `255.255.0.0` is incorrect for an OSPF network command; it's a subnet mask and not a valid wildcard mask in this context.

The wildcard mask `0.0.255.255` is incorrect as it implies a /16 network, which would not match a typical /24 interface subnet, and is not the inverse of a /24 subnet mask.

The wildcard mask `255.255.255` is incomplete; a valid wildcard mask requires four octets, like 0.0.0.0 or 0.0.0.255.