Your network consists of an Active Directory domain that contains the domain controllers shown in the following table. You plan to deploy an Exchange Server 2010 server in each site.  You need to recommend changes to the domain controllers to support the installation of Exchange Server2010. What should you do？（）

• A、Enable Server2 as a global catalog server.
• B、Enable Server3 as a global catalog server.
• C、Upgrade Server2 to Windows Server 2008 SP2 （x64）.
• D、Upgrade Server3 to Windows Server 2008 SP2 （x64）.