Your network consists of a single Active Directory domain. All domain controllers run Windows Server 2003 You upgrade all domain controllers to Windows Server 2008 You need to configure the Active Directory environment to support the application of multiple password policies What should you do（）

• A、Create multiple Active Directory sites.
• B、On all domain controllers， run dcpromo /adv.
• C、On one domain controller， run dcpromo /adv.
• D、Raise the functional level of the domain to Windows Server 2008.