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