A domain controller named DC12 runs critical services. Restructuring of the organizational unit  hierarchy for the domain has been completed and unnecessary objects have been deleted.     You need to perform an offline defragmentation of the Active Directory database on DC12. You  also need to ensure that the critical services remain online.     What should you do（）

• A、Start the domain controller in the Directory Services restore mode. Run the Defrag utility.  
• B、Start the domain controller in the Directory Services restore mode. Run the Ntdsutil utility.
• C、Stop the Domain Controller service in the Services （local） Microsoft Management Console （MMC）. Run the Defrag
• D、Stop the Domain Controller service in the Services （local） Microsoft Management Console （MMC）. Run the Ntdsutil