The correct answer is The active virtual gateway (AVG) will reply with one of four virtual MAC addresses

With GLBP, routers are configured as members of the GLBP group to help load balance traffic. The of the four maximum GLBP member routers, active virtual gateway (AVG) is the most used. The AVG is responsible for replying to ARP requests to local hosts such as workstations, servers, etc., using one of four (in our example) virtual MAC addresses that correspond to different routers