Which domain controller should you identify?

Your network contains an Active Directory forest named contoso.com. The forest contains
two domains. All domain controllers are configured as global catalog servers.
The forest root domain contains five domain controllers. The domain controllers are
configured as shown in the following table.

You plan to create a custom attribute in Active Directory that will replicate to all of the global
catalog servers.
You need to identify which domain controller must be online to perform the planned action.
Which domain controller should you identify?

A.
DC1

B.DC2
C.DC3
D.DC4
E.DC5