Your 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.