Your network consists of one Active Directory domain. The domain contains servers that run Windows Server 2008.

The servers are configured as shown in the following table:

All client computers run Windows Vista Service Pack 1 (SP1).

Remote domain users at a customer site report that they can access Server2 from the Internet by using the URL https://portal.contoso.com.

They also report that a firewall at the customer site prevents all other outbound connections.
You need to implement a solution to enable remote users to access files on Server3 from a VPN connection.

Which connection should you enable on Server1?

A.
IPsec Tunnel mode

B.
L2TP

C.
PPTP

D.
Secure Socket Tunneling Protocol (SSTP)