You need to upgrade Server1 to Windows Server 2012 R2 with the graphical user interface (GUI)

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.
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.

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

C.
OnServer1, 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.

D.
OnServer1, run setup.exe from the Windows Server 2012 R2 installation media and select Server with a
GUI.

Explanation:
You should upgrade to 2012 and install GUI shell. Upgrades that switch from a Server Core installationto the
Server with a GUI mode of Windows Server 2012 in one step (and vice versa) are not supported. However,
after upgrade is complete, Windows Server 2012 allows you to switch freely between Server Core and Server
with a GUI modes.