You have a Windows Server 2008 R2 Hyper-V server with a single network adapter that is connected to a virtual network. The virtual network is configured as External. Virtual machines （VMs） running on the server are not able to communicate with the host server over the network. You need to ensure that VMs running on the server are able to communicate with the host server over the network.  In Virtual Network Manager，what should you do？（）

• A、Select the Internal only connection type.
• B、Select the Private virtual machine network connection type.
• C、Select the Allow management operating system to share this network adapter check box.
• D、Clear the Allow management operating system to share this network adapter check box.