Your network contains two Active Directory forests named contoso.com and adatum.com. Each
forest contains one domain. A two-way forest trust exists between the forests.
The forests use the address spaces shown in the following table.

From a computer in the contoso.com domain, you can perform reverse lookups for the servers in the
contoso.com domain, but you cannot perform reverse lookups for the servers in the adatum.com
domain.

From a computer in the adatum.com domain, you can perform reverse lookups for the servers in
both domains.
You need to ensure that you can perform reverse lookups for the servers in the adatum.com domain
from the computers in the contoso.com domain.
What should you create?

A.
A trust point

B.
A GlobalNames zone

C.
A delegation

D.
A conditional forwarder

Explanation:
Conditional forwarders are DNS servers that only forward queries for specific domain names. Instead
of forwarding all queries it cannot resolve locally to a forwarder, a conditional forwarder is
configured to forward a query to specific forwarders based on the domain name contained in the
query. Forwarding according to domain names improves conventional forwarding by adding a namebased condition to the forwarding process.
The conditional forwarder setting for a DNS server consists of the following:
The domain names for which the DNS server will forward queries.
One or more DNS server IP addresses for each domain name specified.
When a DNS client or server performs a query operation against a DNS server, the DNS server looks
to see if the query can be resolved using its own zone data or the data stored in its cache. If the DNS
server is configured to forward for the domain name designated in the query, then the query is
forwarded to the IP address of a forwarder associated with the domain name. For example, in the
following figure, each of the queries for the domain names is forwarded to a DNS server associated
with the domain name.
http://technet.microsoft.com/en-us/library/cc757172(v=ws.10).aspx