You work as an Exchange Administrator for TechWorld Inc.The company has a Windows 2008 Active Directory-based contains an Exchange Server 2010 organization.You have deployed Hub Transport server， Client Access server， Unti Mailbox server in the messaging organization.You have not deployed any Edge Transport server in the messaging c following servers can be used to receive and send mail traffic to the Internet？（）
- AServer configured with the Client Access server role.
- BServer configured with the Hub Transport role.
- CServer configured with the Mailbox role.
- DServer configured with the Unified Messaging server role.