Your network contains an Active Directory forest.
You need to add a new user principal name (UPN) suffix to the forest.
Which tool should you use?

A.
Active Directory Administrative Center

B.
Active Directory Domains and Trusts

C.
Active Directory Sites and Services

D.
Active Directory Users and Computers

Explanation:
http://www.kassapoglou.com/windows-server-2008-lesson-23-video-creating-a-user/
Demonstration adding a UPN Suffix
To add or modify a UPN suffix for your forest, open Active Directory Domains and Trusts
from the start menu. Right click Active Directory Domains and Trusts at the top and open the
properties. From here you can add and remove additional domain UPN suffixes for the
forest.