You install two Exchange Server 2010 Edge Transport servers named Server1 and Server2.You need to ensure that e-mail sent from the Internet is sent to Server2 if Server1 fails.What should you do？（）

• A、Create two SRV records.Assign the SRV record for Server1 a priority of 20.Assign the SRV record Server2 a priority of 10.
• B、Create two SRV records.Assign the SRV record for Server1 a priority of 10.Assign the SRV record for Server2 a priority of 20.
• C、Create two MX records.Assign the MX record for Server1 a priority of 20.Assign the MX record for Server2 a priority of 10.
• D、Create two MX records.Assign the MX record for Server1 a priority of 10.Assign the MX record for Server2 a priority of 20.