What cost-effective solution component enables branch office workers to continue collaborating
with each other and making external calls even when the corporate network is unavailable?

A.
Survivable Branch Communication Module powered by Lync

B.
Redundant IT Infrastructure at the branch office

C.
HP Intelligent Management Center

D.
Redundant Branch Office Network switches

Explanation:
Reference: http://h17007.www1.hp.com/one/alliance/microsoft/lync.htm