Your network consists of an Active Directory domain. The domain controllers run Windows Server 2008 R2. Client computers run Windows 7.   You need to implement Encrypting File System （EFS） for all client computers. You want to achieve this goal while meeting the following requirements：   èYou must minimize the amount of data that is transferred across the network when a user logs on to or off from a client computer.   èUsers must be able to access their EFS certificates on any client computers. èIf a client computer s disk fails， EFS certificates must be accessible    What should you do？（）

• A、Enable credential roaming.
• B、Enable roaming user profiles.
• C、Enable a Data Recovery Agent.
• D、Issue smart cards to all users.