You need to ensure that DC1 and DC4 are the only servers that replicate Active Directory changes bet

Your network contains an Active Directory domain named contoso.com.

The Active Directory sites are configured as shown in the Sites exhibit. (Click the Exhibit button.)

You need to ensure that DC1 and DC4 are the only servers that replicate Active Directory changes between the sites.

What should you do?

Exhibit:

A.
Configure DC1 as a preferred bridgehead server for IP transport.

B.
Configure DC4 as a preferred bridgehead server for IP transport.

C.
From the DC4 server object, create a Connection object for DC1.

D.
From the DC1 server object, create a Connection object for DC4.

Explanation:
Please Check Answer

Connections. The KCC creates connections that enable domain controllers to replicate with each other. A connection defines a one-way, inbound route from one domain controller, the source, to another domain controller, the destination. The KCC reuses existing connections where it can, deletes unused connections, and creates new connections if none exist that meet the current need.

Bridgehead Servers. To communicate across site links, the KCC automatically designates a single server, called the bridgehead server, in each site to perform site-to-site replication. Subsequent replication occurs by replication within a site. When site links are established, authorized administrators can designate the bridgehead servers that they want to receive replication between sites. By designating a specific server to receive replication between sites, rather than using any available server, authorized administrators can specify the most beneficial conditions for the connection between sites. Bridgehead servers ensure that most replication occurs within sites rather than between sites.

http://technet.microsoft.com/library/dd277429.aspx