What is the best recommendation to achieve the goal?

Your company has two offices. The offices are located in San Francisco and Los Angeles. Each
office contains a data center. Each data center has a local connection to the Internet. You deploy
an Exchange Server 2016 organization named Contoso and install three servers in each data
center. All of the servers are members of a single database availability group (DAG). Each data
center hosts 2,000 mailboxes that replicate to the other data center. You create four records in
DNS. The records are configured as shown in the following table.

You need to recommend a client access solution for the organization to meet the following
requirements: When connecting from the Internet, all users must connect to the same namespace
for Outlook on the Web. If a connection to the Internet fails at one data center, all users must be
able to access their mailbox from the Internet. When connecting from the Internet, all user
connections to Exchange ActiveSync must be balanced equally across both data centers. What is
the best recommendation to achieve the goal? More than one answer choice may achieve the goal.
Select the BEST answer.

A.
in the San Francisco office, configure the internal URLs of the servers to use the internal
URLofsfmail.contoso.com. In the Los Angeles office, configure

B.
in the San Francisco office, configure the external URLs of the servers to use the internal
URLofsfmail.contoso.com. In the Los Angeles office, configure

C.
Deploy a hardware-based load balancer to each office and configure all of the internal URLs to use
mail.contoso.com

D.
Deploy a hardware-based load balancer to each office and configure all of the external URLs to
use mail.contoso.com