You have a single Active Directory directory service domain with three sites named Site1，Site2，and  Site3. There are site links between all three sites，and replication between sites occurs every 30 minutes. You need to ensure that all replication traffic is routed through Site2.  What should you do？（）  

• A、 Define a preferred bridgehead server for Site2.
• B、 Reduce the interval between replications between Site1 and Site2 and between Site2 and Site3.
• C、 Decrease the cost of the site link between Site1 and Site3.
• D、 Increase the cost of the site link between Site1 and Site3.