HOTSPOT
You need to identify the minimum number of Skype for Business Server 2015 servers and supporting server roles required in each Skype for Business site.
What is the minimum number of servers required? To answer, select the appropriate number of each server type in the answer area.
Answer: 
Explanation:
References:
https://technet.microsoft.com/en-us/library/gg615015.aspx
https://blogs.technet.microsoft.com/canitpro/2015/05/05/step-by-step-installation-of-skype-for-business-server-2015/