Your company has a main office and 20 remote offices. The network contains an Active Directory forest. The forest contains domain controllers that run Windows Server 2012 R2. The forest functional level is Windows Server 2008 R2. The company has a Microsoft Exchange Server organization. Most servers have Exchange Server 2013 installed. Three servers in the remote offices have Exchange Server 2010 installed. One quarter of users have voicemail provided by Unified Messaging (UM). You need to deploy an Exchange Server 2019 database availability group (DAG) to the main office. Which two actions should you perform to prepare the organization for the DAG deployment? Each correct answer presents part of the solution. NOTE: Each correct selection is worth one point.
A. Disable UM for all the users.
B. Upgrade all the domain controllers to Windows Server 2019.
C. Create a new Active Directory site for the main office.
D. Raise the forest functional level to Windows Server 2012 R2.
E. Upgrade the remaining Exchange Server 2010 servers to Exchange Server 2013