You need to ensure that all VPN connection requestsare authenticated and authorized by either Server2or Server3

Your network contains an Active Directory domain.
You plan to implement a remote access solution thatwill contain three servers that run Windows Server2012.
The servers will be configured as shown in the following table.

You need to ensure that all VPN connection requestsare authenticated and authorized by either Server2or
Server3. The solution must ensure that the VPN connections can be authenticated if either Server2 or Server3
fails.
What should you do?

A.
On Server1, configure a RADIUS proxy. Add Server2and Server3 to a failover cluster.

B.
Add Server2 and Server3 to a Network Load Balancing (NLB) cluster. On Server1, modify the
Authentication settings.

C.
On Server1, configure a RADIUS proxy. On Server2 and Server3, add a RADIUS client.

D.
On Server2 and Server3, add a RADIUS client. On Server1, modify the Authentication settings.

Explanation:
http://technet.microsoft.com/en-us/library/cc754033.aspx