Your network contains an Active Directory domain named contoso.com. All domain
controllers run Windows Server 2008 R2. The functional level of the domain is Windows
Server 2008 R2. The functional level of the forest is Windows Server 2008.
You have a member server named Server1 that runs Windows Server 2008.
You need to ensure that you can add Server1 to contoso.com as a domain controller.
What should you run before you promote Server1?
A.
dcpromo.exe /CreateDCAccount
B.
dcpromo.exe /ReplicaOrNewDomain:replica
C.
Set-ADDomainMode -Identity contoso.com -DomainMode Windows2008Domain
D.
Set-ADForestMode -Identity contoso.com -ForestMode Windows2008R2Forest
Explanation:
http://technet.microsoft.com/en-us/library/understanding-active-directory-functionallevels.aspx
After you set the domain functional level to a certain value in Windows Server 2008 R2, you
cannot roll back or lower the domain functional level, with one exception: when you raise the
domain functional level to Windows Server 2008 R2 and if the forest functional level is
Windows Server 2008 or lower, you have the option of rolling the domain functional level
back to Windows Server 2008. You can lower the domain functional level only from Windows
Server 2008 R2 to Windows Server 2008. If the domain functional level is set to Windows
Server 2008 R2, it cannot be rolled back, for example, to Windows Server 2003.