Your network consists of an Active Directory forestnamed contoso.com.
All serversrun Windows Server 2008 R2.
All domain controllersare configured as DNS servers.
The contoso.com DNS zone is stored in the ForestDnsZones Active Directory application partition.
You have a member serverthat contains a standard primary DNS zone for dev.contoso.com.
You need to ensure that all domain controllers can resolve names for dev.contoso.com.
What should you do?

A.
Modify the properties of the SOA record in the contoso.com zone.

B.
Create a NS record in the contoso.com zone.

C.
Create a delegation in the contoso.com zone.

D.
Create a standard secondary zone on a Global Catalog server.

Explanation:
http://technet.microsoft.com/en-us/library/cc771640.aspx
Understanding Zone Delegation
Domain Name System (DNS) provides the option of dividing up the namespace into one or more zones, which
can then be stored, distributed, and replicated to other DNS servers. When you are deciding whether todivide
your DNS namespace to make additional zones, consider the following reasons to use additional zones:
You want to delegate management of part of yourDNS namespace to another location or department in
your organization.
You want to divide one large zone into smaller zones to distribute traffic loads among multiple servers,
improve DNS name resolution performance, or create a more-fault-tolerant DNS environment.
You want to extend the namespace by adding numerous subdomains at once, for example, to
accommodate the opening of a new branch or site.
..
When you delegate zones within your namespace, remember that for each new zone that you create, you need
delegation records in other zones that point to theauthoritative DNS servers for the new zone. This is
necessary both to transfer authority and to providecorrect referral to other DNS servers and clients of the new
servers that are being made authoritative for the new zone.
..
Example: Delegating a subdomain to a new zone
As shown in the following illustration, when a new zone for a subdomain (example.microsoft.com) is created,
delegation from the parent zone (microsoft.com) is needed.