问题：

[单选]

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.