Answer:
Option D i.e., PDC emulator master is the correct answer.
Step-by-step explanation:
In the following statement, the operation master role is maintained by the PDC(Primary Domain controller) emulator master that is important for support that type of compatibility which is backward with the server of the Windows NT network that configured as Controllers or User Servers for Windows NT backup.
Other option is not correct because the following statement is related to the PDC emulator master.