问题：

[单选]

You are the network administrator for Northwind Traders. The network consists of a single Active Directory forest that contains one root domain and one child domain. The forest also contains three separate sites， as shown in the Network Diagram exhibit. （Click the Exhibit button.） The network is not fully routed and there is no direct physical connection between Site1 and Site3. Site links are not bridged. You discover that the domain controllers for namerica.northwindtraders.com located in Site1 have additional accounts that are not on the domain controllers for namerica.northwindtraders.com located in Site3. You examine the directory service log in Event Viewer on a domain controller for namerica.northwindtraders.com. You discover the error message shown in the Error Message exhibit. （Click the Exhibit button.） You need to resolve the condition that is causing this error. 
What should you do？ （）

A .  Add a domain controller for the namerica.northwindtraders.com domain to Site2.
B .  Configure a site link bridge between the site links for Site1 and Site3.
C .  Configure at least one domain controller in each site to be a global catalog server.
D .  Create a site link between Site1 and Site3.