How do IPv6 unicast and anycast addresses differ?

The correct answer accurately distinguishes between unicast and anycast addresses. An IPv6 unicast address uniquely identifies a single interface on a single node, meaning a packet sent to this address goes to that specific interface. In contrast, an IPv6 anycast address is assigned to multiple interfaces, typically on different nodes, and a packet sent to an anycast address is delivered to the nearest interface (according to the routing protocol's definition of "nearest"). The second and third options are incorrect because neither unicast nor anycast addresses inherently require special configuration beyond standard IP address assignment. The fourth option incorrectly describes a unicast address as being assigned to a group of interfaces on multiple nodes, which is characteristic of anycast, not unicast.