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.
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.