Your network contains an Active Directory forest. The forest contains a single domain named contoso.com. The domain contains four domain controllers. The domain controllers are configured  as shown in the following table. You plan to deploy a new domain controller named DC5 in the contoso.com domain. You need to identify which domain controller must be online to ensure that DC5 can be promoted  successfully to a domain controller.  Which domain controller should you identify？（）

• A、DC1
• B、DC2
• C、DC3
• D、DC4