Your company has a Windows Server 2003 Active Directory forest that contains a single domain. The functional level of the forest is set to Windows 2000 native.  You have an Exchange organization that contains Exchange Server 2003 Service Pack 2 （SP2） and Exchange Server 2007 Service Pack 2 （SP2） servers.  You plan to transition the organization to Exchange Server 2010.  You need to prepare Active Directory for the installation of the first Exchange Server 2010 server.  What should you do（）？

• A、Set the functional level of the forest to Windows Server 2003.
• B、Prepare the legacy Exchange permissions from the Exchange Server 2010 installation source files.
• C、Add the Exchange Server 2010 schema extensions by using the Exchange Server 2010 installation source files.
• D、Upgrade all domain controllers to Windows Server 2008， and then set the functional level of the domain to Windows Server 2008.