Your company, Contoso, Ltd., has a main officeand a branch office.
The officesare connected by a WAN link.
Contoso has an Active Directory forestthat containsa single domainnamed ad.contoso.com.
The ad.contoso.com domain contains one domain controllernamed DC1that is located in the main office.
DC1is configured as a DNS serverfor thead.contoso.com DNS zone.
This zoneis configuredas a standard primary zone.
You install a new domain controllernamed DC2in the branch office.
You install DNSon 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 secondary zone named ad.contoso.com on DC2.

B.
Create a new stub zone named ad.contoso.com on DC2.

C.
Configure the DNS server on DC2 to forward requests to DC1.

D.
Convert the ad.contoso.com zone on DC1 to an Active Directory-integrated zone.

Explanation:
Three answers don’t make sense, leaving us with theone that works.
Create a new secondary zone named ad.contoso.com onDC2.
This would create a read-only zone, so it couldn’t be updated
Create a new stub zone named ad.contoso.com on DC2.
This stub zone would contain source information about authoritative name servers for its zone only, being DC1,
but that one would be unavailable in the WAN link fails.
Configure the DNS server on DC2 to forward requeststo DC1.
This doesn’t help if the WAN link fails and DC1 is unavailable.