You work as the enterprise exchange administrator at TestKing.com. TestKing.com makes use of
Microsoft Exchange Server messaging solution. The TestKing.com network consists of a single ActiveDirectory forest that contains two domains and one site. The funcitional level of the forest is set at
Windows Server 2003. TestKing.com has a headquarters and two offices that are connected to each other via a WAN link. Furthermore， all these three offices have a direct link to the Internet. The domain controllers are configured as global catalog servers and runs Windows Server 2003 R2.
All these three offices contain two global catalog servers. During the course of the day you receive aninstruction to install Mailbox， Client Access and Hub Transport Exchange Server 2010 servers in all these offices. One local server will be utilized at every office to send e-mail to the Internet. To ensure
productivity you need to propose the necessary modifications to the Active Directory environment in order to supprt the installation.
What should you do？（）

A.This can be accomplished by ensuring that the site link building for the forest is disabled.
B.This can be accomplished by ensuring that the cost values for the default IP site link are changed.
C.This can be accomplished by ensuring that an Active Directory subnet as well as a site object iscreated for every office.
D.This can be accomplished by ensuring that one global catalog server in every office is upgraded to Windows Server 2008.