You deploy mobile devices that run Microsoft Windows Mobile 5.0. Users will use MSN Messenger on the devices.   You need to ensure that users use their corporate e-mail accounts to sign in to the MSN Messenger service.   What should you do？（）

• A、Instruct users to register for an MSN Messenger e-mail account.
• B、Instruct users to reset the passwords for their domain user accounts.
• C、Instruct users to clear all saved passwords on their Windows Mobilebased devices.
• D、Instruct users to register for a valid MSN Messenger account by using their corporate e-mail addresses.