What should you recommend? (More than one answer choice may achieve the goal

A company has servers that run a Server Core installation of Windows Server 2008.

You are designing the migration of the servers to Windows Server 2008 R2. After the migration, you will install the Remote Desktop Services server role and the Print and Document Services server role on the servers.
You need to ensure that shared resources on the servers are available after the migration, and minimize administrative effort.

What should you recommend? (More than one answer choice may achieve the goal. Select the BEST answer.)

A.
Deploy new servers with a Server Core installation of Windows Server 2008 R2. Migrate the shared resources to the new servers.

B.
Upgrade the existing servers to a Server Core installation of Windows Server 2008 R2, and then upgrade the servers to a full installation of Windows Server 2008 R2.

C.
Move the shared resources off of the existing servers. Perform a clean installation of Windows Server 2008 R2 on the servers. Move the shared resources back onto the servers.

D.
Deploy new servers with Windows Server 2008 R2 installed. Migrate the shared resources to the new servers.

Explanation:
the key here is minimize effort & Remote Desktop Services.
Server Core wouldn’t allow remote desktop services as it has no GUI so that would rule out answer A
you also cant upgrade from Core to Full see http://www.windowsitpro.com/article/tips/can-i-upgrade-from-server-core-2008-to-the-full-windows-server-2008- or http://serverfault.com/questions/92523/upgrade-from-windows-2008-server-core-to-full-windows-2008-server
upgrade considerations for Server Core installations of Windows Server 2008 so that rules our B

You can use the Server Core installation option only by performing a clean installation.
You cannot upgrade from earlier versions of Windows to Server Core installations of Windows Server 2008.
You cannot upgrade from non-Server Core installations of Windows Server 2008 to Server Core installations of Windows Server 2008.
You cannot convert Server Core installations of Windows Server 2008 to non-Server Core installations of Windows Server 2008.
You can upgrade Server Core installations of Windows Server 2008 only to Windows Server Core R2 when it is released.

Answer C is possible but again you’re asked to mimimise effort so D would be 1 step less thus reducing your effort and possible down time.