Your network consists of a single Active Directory domain. All domain controllers run Windows Server  2008 R2 and are configured as DNS servers. A domain controller named DC1 has a standard primary  Zone for contoso.com. A domain controller named DC2 has a standard secondary zone for contoso.com.   You need to ensure that the replication of the contoso.com zone is encrypted. You must not lose any zone  data.  What should you do（）

• A、On both servers， modify the interface that the DNS server listens on.
• B、Convert the primary zone into an Active Directory-integrated zone. Delete the secondary zone.  
• C、Convert the primary zone into an Active Directory-integrated stub zone. Delete the secondary zone.
• D、Configure the zone transfer settings of the standard primary zone. Modify the Master Servers lists on  the secondary zone.