Your company has a main office and a branch office. The main office contains two domain  controllers.   You create an Active Directory site named BranchOfficeSite.    You deploy a domain controller in the branch office， and then add the domain controller to the  BranchOfficeSite site. You discover that users in the branch office are randomly authenticated by either the domain controller in   the branch office or the domain controllers in the main office.   You need to ensure that the users in the branch office always attempt to authenticate to the domain  controller in the branch office first.   What should you do（）

• A、Create organizational units （OUs）.
• B、Create Active Directory subnet objects.
• C、Modify the slow link detection threshold.
• D、Modify the Location attribute of the computer objects.