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？（）