Your company has a main office and a branch office. The branch office contains a read-only  domain controller named RODC1.     You need to ensure that a user named Admin1 can install updates on RODC1. The solution must  prevent Admin1 from logging on to other domain controllers.     What should you do（）

• A、Run ntdsutil.exe and use the Roles option.
• B、Run dsmgmt.exe and use the Local Roles option.
• C、From Active Directory Sites and Services， modify the NTDS Site Settings.
• D、From Active Directory Users and Computers， add the user to the Server Operators group.