What should you use?

Your network contains an Active Directory forest.
You add an additional user principal name (UPN) suffix to the forest. You need to modify the UPN suffix of all users. You want to achieve this goal by using the minimum amount of administrative effort.
What should you use?

A.
the Active Directory Domains and Trusts console

B.
the Active Directory Users and Computers console

C.
the Csvde tool

D.
the Ldifde tool