问题：

[单选] Your company has an Active Directory domain. You log on to the domain controller. The Active Directory Schema snap-in is not available in the Microsoft Management Console （MMC）. You need to access the Actrve Directory Schema snap-in. What should you do（）

A . Register Schmmgml.dll.
B . Log off and log on again by using an account that is a member of the Schema Administrators group.
C . Use the Ntdsutil.exe command to connect to the Schema Master operations master and open the schema for writing.
D . Add the Active Directory Lightweight Directory Services （AD LDS） role to the domain controller by using Server Manager.