You have a server named Server1 that has a Server Core installation of Windows Server 2008 R2.
Server1 has the DHCP Server server role and the File Server server role installed.
You need to upgrade Server1 to Windows Server 2012 R2 with the graphical user interface (GUI).
The solution must meet the following requirements:
Preserve the server roles and their configurations.
Minimize administrative effort.
What should you do?

A.
On Server1, run setup.exe from the Windows Server 2012 R2 installation media and select Server
with a GUI.

B.
Start Server1 from the Windows Server 2012 R2 installation media and select Server Core
Installation.

When the installation is complete, add the Server Graphical Shell feature.

C.
Start Server1 from the Windows Server 2012 R2 installation media and select Server with a GUI.

D.
On Server1, run setup.exe from the Windows Server 2012 R2 installation media and select Server
Core Installation.
When the installation is complete, add the Server Graphical Shell feature

Explanation:
A)
Server is on 2008 R2 core, must install 2012 R2 core and then GUI
B)
Not least effort
C)
Not least effort
D)
Upgrade to 2012 R2 and install GUI shell
http://technet.microsoft.com/en-us/library/jj574204.aspx Upgrades that switch from a Server Core
installation to the Server with a GUI mode of Windows Server 2012 R2 in one step (and vice versa)
are not supported.
However, after upgrade is complete, Windows Server 2012 R2 allows you to switch freely between
Server Core and Server with a GUI modes.