You have an Exchange Server 2010 organization.  You have a global security group named Legal that contains all the members of your companys legaldepartment.  The companys security policy states that the Legal group must be able to search all mailboxes for e-mailmessages that contain specific keywords.  You need to recommend a solution for the organization that complies with the security policy.  What should you include in the solution？（）

• A、a Discovery Management role group
• B、a legal hold
• C、administrator audit logging
• D、Mailbox journaling