Correct Answer:
Explanation/Reference:
. Active Directory Domain Services (AD DS) defines five operations master roles: the schema master, domain naming master, relative identifier (RID) master, primary domain controller (PDC) emulator, and infrastructure master. The domain controllers that hold operations master roles are designated to perform specific tasks to ensure consistency and to eliminate the potential for conflicting entries in the AD DS database.
. A server can have more than one operations master role.
. Forestwide Operations Master Roles
The schema master and domain naming master are forestwide roles, meaning that there is only one schema master and one domain naming master in the entire forest.
. Domainwide Operations Master Roles
The other operations master roles are domainwide roles, meaning that each domain in a forest has its own RID master, PDC emulator, and infrastructure master.
Reference: What are Operations Masters?
https://technet.microsoft.com/en-us/library/cc779716%28v=ws.10%29.aspx