Use B for this item. A DHCP helper address is configured on the Layer 3 interface that receives the client broadcast. The first-hop router closest to the client converts DHCP broadcast traffic into unicast traffic toward the DHCP server. In Cisco CCNA 200-301 v1.1, IP Services 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. Putting the command near the server, on every router, or on a switch trunk does not intercept the original client DHCPDISCOVER broadcast correctly. 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.