Your company has an Active Directory domain named ad.contoso.com. The domain has two  domain controllers named DC1 and DC2. Both domain controllers have the DNS Server server  role installed.     You install a new DNS server named DNS1.contoso.com on the perimeter network. You  configure DC1 to forward all unresolved name requests to DNS1.contoso.com.   You discover that the DNS forwarding option is unavailable on DC2. You need to configure DNS  forwarding on the DC2 server to point to the DNS1.contoso.com server. Which two actions should  you perform（）

• A、Clear the DNS cache on DC2.
• B、Delete the Root zone on DC2.
• C、Configure conditional forwarding on DC2.
• D、Configure the Listen On address on DC2.