You install two Exchange Server 2010 Service Pack 1 （SP1） Edge Transport servers named Edge1 and Edge2.You need to ensure that e-mail is sent only to Edge2 if Edge1 fails. What should you do？（）

• A、Create two CNAME records that have the same name.Create one MX record that uses the FQDN of the CNAME records.Assign a priority of 0 to the MX record.
• B、Create two MX records.Assign the MX record for Edge1 a priority of 5.Assign the MX record for Edge2 a priority of 1.
• C、Create two A records that use the same name.Create one MX record that uses the FQDN of the A record.Assign a priority of 0 to the MX record.
• D、Create two MX records.Assign the MX record for Edge1 a priority of 1.Assign the MX record for Edge2 a priority of 5.