our network consists of a single Active Directory domain. You have a domain controller and a  member server that run Windows Server 2008 R2. Both servers are configured as DNS servers.  Client computers run either Windows XP Service Pack 3 or Windows 7. You have a standard  primary zone on the domain controller. The member server hosts a secondary copy of the zone.     You need to ensure that only authenticated users are allowed to update host （A） records in the  DNS zone.     What should you do first（）

• A、On the member server， add a conditional forwarder.
• B、On the member server， install Active Directory Domain Services.
• C、Add all computer accounts to the DNSUpdateProxy group.
• D、Convert the standard primary zone to an Active Directory-integrated zone.