You have an Exchange organization that contains the Exchange servers shown in the
following table. You plan to move all mailboxes from Server2 to Server3. You need to ensure
that all users can send and receive e-mail messages after their mailboxes are moved to
Server3.

What should you do?

A.
Install the Exchange Server 2010 Hub Transport server role.

B.
Install the Exchange Server 2010 Edge Transport server role.

C.
Remove all Exchange Server 2003 servers.

D.
Remove the Exchange Server 2003 front-end server. Install a new Exchange Server 2010
Client Access server.

Explanation:

http://technet.microsoft.com/en-us/library/aa998604.aspx