Your company has two Active Directory forestsnamed contoso.comand fabrikam.com.
The company networkhas three DNS serversnamed DNS1, DNS2, and DNS3.
The DNS servers are configured as shown in the following table:

All computers that belong to the fabrikam.com domain have DNS3 configured as thepreferred DNS server.
All other computers useDNS1 as the preferred DNS server.
Users from thefabrikam.com domain are unable to connect to theservers that belong to thecontoso.com
domain.
You need to ensure users in the fabrikam.com domain areable to resolve all contoso.com queries.
What should you do?

A.
Configure conditional forwarding on DNS1 and DNS2to forward fabrikam.com queries to DNS3.

B.
Create a copy of the _msdcs.contoso.com zone on the DNS3 server.

C.
Create a copy of the fabrikam.com zone on the DNS1 server and the DNS2 server.

D.
Configure conditional forwarding on DNS3 to forwardcontoso.com queries to DNS1.

Explanation:
http://technet.microsoft.com/en-us/library/cc730756.aspx
Understanding Forwarders
A forwarder is a Domain Name System (DNS) server ona network that forwards DNS queries for external DNS
names to DNS servers outside that network. You can also forward queries according to specific domain names
using conditional forwarders.
You designate a DNS server on a network as a forwarder by configuring the other DNS servers in the network
to forward the queries that they cannot resolve locally to that DNS server. By using a forwarder, you can
manage name resolution for names outside your network, such as names on the Internet, and improve the
efficiency of name resolution for the computers in your network.
The following figure illustrates how external name queries are directed with forwarders.

…
Conditional forwarders
A conditional forwarderis a DNS server on a network that forwards DNS queries according to the DNS
domain name in the query. For example, you can configure a DNS server to forward all the queries that it
receives for names ending with corp.contoso.com to the IP address of a specific DNS server or to the IP
addresses of multiple DNS servers.