Trey Research has a Lync 2013 environment that consists of a single Enterprise Edition pool with five Front End Servers,

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Trey Research has a Lync 2013 environment that consists of a single Enterprise Edition pool with five Front End Servers, and two SQL Servers in a mirroring relationship.
The company plans to upgrade to Skype for Business Server 2015. You install the Skype for Business Server 2015 Administrative tools on a management workstation. You install all server prerequisites. There can be downtime during the migration. You must minimize the risk of upgrade failure due to services restarting during the upgrade process.
You need to upgrade the Enterprise Edition pool.
Which two actions should you perform? Each correct answer presents part of the solution.

A. RunSetup.exe on each computer in the pool. Run the Start-CsPoolSkype for Business Management Shell cmdlet on one Front End server in the pool.
B. Upgrade and publish the topology. Run the Stop-CsWindowsServiceLync Management Shell cmdlet on all computers in the pool.
C. RunSetup.exe on each computer in the pool. Run the Start-CsWindowsServiceSkype for Business Management Shell cmdlet on all Front servers in the pool.
D. Upgrade and publish the topology. Run theDisable-CsComputer –ScorchLync Management Shell cmdlet on all computers in the pool.