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？（）
- AAdd User1 to Group1 Managed by list
- BAssign User1 as a group moderator for Group1.
- CAssign the Message Tracking management role to User1.
- DAdd User1 to Group1 and then create a new journal rule.