You plan to install Exchange Server 2010 Service Pack 1 (SP1) servers in an existing Exchange Server 2007 organization.All servers will coexist in a single Active Directory site. You need to identify which role must be transitioned to Exchange Server 2010 first. Which role should you identify?()
- AHub Transport.
- BMailbox Server.
- CUnfied Messaging.
- DClient Access Server.