Your network consists of an Active Directory domain and a DirectAccess infrastructure. You install Windows7 on a new portable computer and join the computer to the domain. You need to ensure that the computercan establish DirectAccess connections.  What should you do?（）

• A、Install a computer certificate.
• B、Create a new network connection.
• C、Enable the Network Discovery firewall exception.
• D、Add the computer account to the Network Configuration Operators group.