How does the ERX Edge Router interact with subscriber IP addresses assigned by an external DHCP server?（）

• A、It monitors messages from the external server and updates the routing table as needed.
• B、It maintains the leases for the DHCP server and reassigns addresses to new subscribers.
• C、It sends keep alives to the subscriber and makes the address available when the subscriber stops responding.
• D、It sends keep alives to the subscriber and removes the host route when the subscriber stops responding.