Which server should you add as a trusted application server?

Your network contains four servers.
The servers are configured as shown in the following table.

You need to configure Lync Server 2010 for Outlook Web App and IM integration.
From the Lync Server Management Shell, you create a trusted application pool.
Which server should you add as a trusted application server?

A.
Server1

B.
Server2

C.
Server3

D.
Server4

E.
Server5

Explanation:
http://technet.microsoft.com/en-us/library/gg413079.aspx