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（）  

Your network contains a server that runs Windows Server 2008 R2. The server is configured as an  
enterprise root certification authority (CA).  
You have a Web site that uses x.509 certificates for authentication. The Web site is configured to use a  
many-to-one mapping.  
You revoke a certificate issued to an external partner.  
You need to prevent the external partner from accessing the Web site.  What should you do（）