You work as the enterprise exchange administrator at Xxx .The Xxx network consists of a domain named xxx .Xxx has acquired a new server named XXX-EX01 that is running Microsoft Exchange Server 2010.What actions must you take to allow the employees to access XXX-EX01 via the Internet by utilizing Exchange ActiveSync？（）

• A、You must enable recipient filtering.
• B、You must use Send connectors.
• C、You must use the Microsoft-Server-ActiveSync virtual directory’s external URL and change it.
• D、You must use DNS forwarding.