Your network includes the servers shown in the following table. Server n ame Operating s ystem Role s ervices S erver 1 Windows Server 2008 Standard TS Licensing S erver 2 Windows Server 2008Enterprise Terminal Server You install an additional server named Server3 that runs Windows Server 2008 R2 Enterprise. You add the Remote Desktop Services （RDS） role， and you configure the Remote Desktop Session Host （RD Session Host） role service. You need to ensure that RDS client access licenses （RDS CALs） can be assigned to each Remote Desktop user. What should you do？（）

• A、Add RDS CALs to Server1.
• B、Specify the Remote Desktop Licensing （RD Licensing） mode on Server3.
• C、Add the Remote Desktop Licensing （RD Licensing） role service to Server3.
• D、Upgrade Server1 from Windows Server 2008 Standard to Windows Server 2008 R2 Enterprise.