Your network has federation enabled with networks that run Microsoft Office Communications Server 2007 R2 and Windows Live. You plan to deploy a Lync Server 2010 Edge pool that will contain three servers. You need to plan a deployment solution to ensure that the Edge services are available if a server fails. What should you include in the plan?

A.
two hardware load balancers on the internal side of the perimeter networktwo reverse proxies on the external side of the perimeter network

B.
one hardware load balancer on the internal side of the perimeter networkDNS load balancing on the external side of the perimeter network

C.
one hardware load balancer on the internal side of the perimeter networkone hardware load balancer on the external side of the perimeter network

D.
one hardware load balancer on the external side of the perimeter networktwo reverse proxies on the external side of the perimeter network

Explanation:
Reference Architecture 3: Scaled Consolidated Edge (Hardware Load Balanced). Hardware load balancing is used for traffic to both the external and internal Edge interfaces. (http://technet.microsoft.com/en-us/library/gg398478.aspx)
You cannot use DNS load balancing on one interface and hardware load balancing on another. You must use hardware load balancing on both interfaces or DNS load balancing for both. A combination is not supported. (http://technet.microsoft.com/en-us/library/gg425779.aspx)