You work as the enterprise exchange administrator at Xxx .Xxx is using Microsoft Exchange Server 2010 as their messaging solution.You have received instructions from the CIO to enable Autodiscover for Internet users by creating a resource record in DNS.What actions must you take？（）

• A、You must set up recipient filtering.
• B、You must set up a Host （A）.
• C、You must use a TXT record.
• D、You must use a Pointer （PTR） record.
• E、You must use a Mail exchange （MX） record.