You have an Exchange Server 2010 organization that contains three servers. The servers are configured as
shown in the following table.

Microsoft Outlook is configured to connect to an FQDN of mail.adatum.com. Mail.adatum.com resolves to the
IP address of a Layer 7 hardware load balancer. The hardware load balancer is configured to send traffic to
EX2 and EX3.
You deploy an Exchange Server 2013 Mailbox server named EX4 and an Exchange Server 2013 Client Access
server named EX5.
You plan to migrate all mailboxes to Exchange Server 2013.
You need to recommend a solution to ensure that users can access their mailbox on EX1 or EX4 during the
migration.
What should you do?

A.
Create a Client Access server array that contains EX1 and EX5.

B.
Modify the autodiscover.contoso.com resource record to point to EX5.

C.
Modify the properties of the hardware load balancer to point to EX5.

D.
Create a DNS record named legacy.contoso.com in the internal DNS zone.

Explanation:
Note: So what is the Client Access server in Exchange 2013? The Client Access server role is comprised of
three components, client protocols, SMTP, and a UM Call Router. The CAS role is a thin, protocol session
stateless server that is organized into a load balanced configuration. Unlike previous versions, session affinity is
not required at the load balancer (but you still want a load balancer to handle connection management policies
and health checking). This is because logic now exists in CAS to authenticate the request, and then route the
request to the Mailbox server that hosts the active copy of the mailbox database.
The Mailbox server role now hosts all the components and/or protocols that process, render and store the data.
No clients will ever connect directly to the Mailbox server role; all client connections are handled by the Client
Access server role.
Exchange 2013 Server Role Architecture