Your network contains an Active Directory domain controller named DC1. DDC1 runs Windows  Server 2008 R2.   You need to defragment the Active Directory database on DC1. The solution must minimize  downtime on DC1.     What should you do first（）

• A、At the command prompt， run net stop ntds.
• B、At the command prompt， run net stop netlogon.
• C、Restart DC1 in Safe Mode.
• D、Restart DC1 in Directory Services Restore Mode （DSRM）.