Use A for this item. RFC 1918 private address space was defined to conserve public IPv4 addresses. Organizations can reuse private ranges internally and translate at the edge with NAT when Internet access is needed. In Cisco CCNA 200-301 v1.1, Network Fundamentals questions frequently test the practical boundary between similar features: what the feature does, where it is configured, and what problem it is meant to solve. It was not designed to preserve IPv6 space or eliminate overlap between private organizations. A clean way to validate the answer is to map the wording of the scenario to the actual device function. If the feature supplies addressing, forwarding, authentication, trunking, route selection, or controller communication, the answer must match that function exactly rather than a nearby protocol name.