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（）

A. Create a new stub zone named ad.contoso.com on DC2.
B. Configure the DNS server on DC2 to forward requests to DC1.
Create a new secondary zone named ad.contoso.com on DC2.
D. Convert the ad.contoso.com zone on DC1 to an Active Directory-integrated zone.