You have an Active Directory forest. You plan to deploy an Exchange Server 2010 organization that contains the following servers：.Two Edge Transport servers.Two Hub Transport servers You need to recommend changes to the organization to ensure that e-mail messages can be sent to the Internet if a single transport server fails. What should you recommend？（）

A. Configure shadow redundancy for the Hub Transport servers.
B. Implement failover clustering on both Hub Transport servers.
Configure both Edge Transport servers as source servers for a Send connector.
D. Create one mail exchange （MX） record and one SRV record for each Edge Transport server on the internal DNS zone.