Your company has an Active Directory Domain Services (AD DS) domain. All servers run Windows Server 2008 R2. You have a Remote Desktop Services infrastructure that hosts remote desktop sessions for users. You need to be able to revoke 240 Remote Desktop Services client access licenses (RDS CALs). What should you do?（）

• A、Configure the Remote Desktop Session Host (RD Session Host) server to use Per User licensing mode.Install 100 RDS CALs.
• B、Configure the Remote Desktop Session  Host (RD Session Host) server to use Per User licensing mode. Install 20 RDS CALs.
• C、Configure the Remote Desktop Session Host (RD Session Host) server to use Per Device licensing mode. Install 20 RDS CALs.
• D、Configure the Remote Desktop Session Host (RD S ession Host) server to use Per Device licensing mode. Install 100 RDS CALs.