You deploy a Microsoft Windows Mobile 5.0 for Smartphonebased mobile messaging solution that has two-tier authentication with Microsoft Exchange Server 2003 Service Pack 2.   Company security policy requires that only company-approved applications are allowed to run on Windows Mobile 5.0 for Smartphonebased devices.   You need to ensure that third-party applications are prevented from running.   Which two actions should you perform？（）

• A、A
• B、B
• C、C
• D、D