You have a hosted Exchange organization.All servers in the organization have Exchange Server 2010 Service Pack 1 （SP1） installed.You need to prevent a user named User1 from using Outlook Web App （OWA） to access his mailbox. What should you do？（）

• A、From the properties of User1’s mailbox， modify the mailbox settings.
• B、From the properties of User1’s mailbox， modify the mailbox features.
• C、Create a new OWA mailbox policy.
• D、Modify the default OWA mailbox policy.