Your network contains a Web-based application that runs on Windows Server 2003. You plan to  migrate the Web-based application to Windows Server 2008 R2. You need to recommend a server  configuration to support the Web-based application. The server configuration must meet the following  requirements：   èEnsure that the application is available to all users if a single server？fails èSupport the installation of .NET applications èMinimize software costs  What should you recommend？（） 

• A、Install the Server Core installation of Windows Server 2008 R2 Standard on two servers. Configure the servers in a Network Load Balancing cluster.
• B、Install the full installation of Windows Server 2008 R2 Web on two servers. Configure the servers in a Network Load Balancing cluster.
• C、Install the full installation of Windows Server 2008 R2 Enterprise on two servers. Configure the servers in a failover cluster.
• D、Install the full installation of Windows Server 2008 R2 Datacenter on two servers. Configure the servers in a failover cluster.