单项选择题 Your company has a main office and a branch office. The company has a single-domain Active  Directory forest.   The main office has two domain controllers named DC1 and DC2 that run Windows Server 2008  R2. The branch office has a Windows Server 2008 R2 read-only domain controller （RODC）named DC3. All domain controllers hold the DNS Server server role and are configured as Active  Directory- integrated zones. The DNS zones only allow secure updates.     You need to enable dynamic DNS updates on DC3.     What should you do（）

单项选择题 Your company has two domain controllers that are configured as internal DNS servers. All zones  on the DNS servers are Active Directory-integrated zones. The zones allow all dynamic updates.  You discover that the contoso.com zone has multiple entries for the host names of computers  that do not exist.     You need to configure the contoso.com zone to automatically remove expired records.     What should you do（）

单项选择题 Your company， Contoso， Ltd.， has a main office and a branch office. The offices are connected  by a WAN link. Contoso has an Active Directory forest that contains a single domain named  ad.contoso.com.     The ad.contoso.com domain contains one domain controller named DC1 that is located in the  main office. DC1 is configured as a DNS server for the ad.contoso.com DNS zone. This zone is  configured as a standard primary zone.   You install a new domain controller named DC2 in the branch office. You install DNS on DC2.  You need to ensure that the DNS service can update records and resolve DNS queries in the  event that a WAN link fails.     What should you do（）