Your company has an Exchange 2010 organization that contains multiple Hub Transport servers. You have a line-of-business application that relays e-mail messages by using a Hub Transport servernamed Hub1. The application only supports sending e-mail to a single SMTP server. You need to ensure that the application can relay e-mail messages if Hub1 fails. What should you do？（）
- AImplement log truncation
- BInstall and configure failover clustering on the Hub Transport servers.
- CImplement Windows network load balancing on the Hub Transport servers.
- DCreate multiple MX records for the Hub Transport servers in the internal DNS zone.