Your network contains a Windows Server 2008 R2 server that functions as a file server. All users have laptop computers that run Windows 7. The network is not connected to the Internet. Users save files to a shared folder on the server. You need to design a data provisioning solution that meets the following requirements： èUsers who are not connected to the corporate network must be able to access the files and the folders in the corporate network. èUnauthorized users must not have access to the cached files and folders. What should you do？（）

A. Implement a certification authority （CA）. Configure IPsec domain isolation.
B. Implement a certification authority （CA）. Configure Encrypting File System （EFS） for the drive that hosts the files.
C. Implement Microsoft SharePoint Foundation 2010. Enable Secure Socket Layer （SSL） encryption.
D. Configure caching on the shared folder. Configure offline files to use encryption.