Your network contains an Active Directory domain named contoso.com. The network contains a
domain controller named DC1 that has the DNS Server server role installed. DC1 has a standard
primary DNS zone for contoso.com.
You need to ensure that only client computers in the contoso.com domain will be able to add their
records to the contoso.com zone.
What should you do first?

A.
Sign the contoso.com zone.

B.
Modify the Security settings of DC1.

C.
Modify the Security settings of the contoso.com zone.

D.
Store the contoso.com zone in Active Directory.

Explanation:
Only Authenticated users can create records when zone is stored in AD.
Secure dynamic updates allow an administrator to control what computers update what names and
prevent unauthorized computers from overwriting existing names in DNS.
References:

Training Guide: Installing and Configuring Windows Server 2012 R2: Chapter 6: Network
Administration, Lesson 2: Implementing DNSSEC, p. 237
http://technet.microsoft.com/en-us/library/cc731204(v=ws.10).aspx
http://technet.microsoft.com/en-us/library/cc755193.aspx