正解:C
The correct response is C. FHRPs improve availability by providing automatic default-gateway redundancy.
If the active gateway fails, another router can take over the virtual IP and MAC so hosts keep using the same default gateway. For Cisco CCNA 200-301 v1.1, the important point is the mechanism, not a generic description of the technology. They do not primarily reduce management overhead, reduce ARP, or perform proportional load balancing in every implementation. When this appears in a network, the symptom normally confirms the answer: the route installed, the state selected, the packet forwarded, the wireless client behaviour, or the management workflow will follow this rule. That is why this answer is the best fit for the scenario and not just a plausible networking term.