You have an Exchange Server 2010 organization.The organization contains a distribution group named Group1.You need to ensure that a user named User1 can review and approve all messages sent to Group1.You must prevent User1 from modifying the membership of Group1.  What should you do？（）

• A、Add User1 to Group1 Managed by list
• B、Assign User1 as a group moderator for Group1.
• C、Assign the Message Tracking management role to User1.
• D、Add User1 to Group1 and then create a new journal rule.