You have an Exchange Server 2010 organization.You create a distribution group for all users in your company.You need to ensure that new users can add their mailboxes to the distribution group.What should you do？（）

• A、Modify the group scope of the distribution group.
• B、Modify the approval mode of the distribution group.
• C、Modify the security settings of the distribution group.
• D、Modify the authentication settings of the ECP virtual directory.