You have an Exchange organization that contains an Exchange Server 2003 SP2.All servers are members of one Administrative Group and one Routing Group. You plan to transition the organization to Exchange Server 2010. You need to prepare the Exchange organization for the deployment of Exchange Server 2010 mailbox， Client Access and Hub Transports servers. What should you do first？（）
- ADisable all link state updates.
- BCreate a Routing Group connector.
- CModify the Active Directory schema.
- DDelete all Recipient Update Service （RUS） objects.