You have an Exchange organization. All servers in the organization have Exchange Server
2010 SP1 installed.
The network contains two Active Directory sites named Site1 and Site2. Only Site1 is
connected to the Internet.
Site1 contains five Client Access servers and a Client Access server array named
array1.contoso.com.
Users connect to their mailboxes by using Outlook Web App (OWA) from the internal
network and from the Internet.
You plan to deploy two Client Access servers and a Client Access server array in Site2.
You need to configure the namespaces for the OWA virtual directories.
What should you do on all of the Client Access servers in Site2?

A.
Set the InternalURL to array2.contoso.com. Set the ExternalURL to array1.contoso.com.

B.
Set the InternalURL to the Client Acess server name. Set the ExternalURL to
array1.contoso.com.

C.
Set the InternalURL to the Client Access server name. Set the ExternalURL to $null.

D.
Set the InternalURL to array2.contoso.com. Set the ExternalURL to $null.

Explanation:
We have an array in Site2, therefore we would need to set the InternalURL to the name of
the array. We can assume the array’s name will be array2.contoso.com.

http://technet.microsoft.com/en-us/library/bb310763.aspx (Proxying with Network Load
Balancing)