A financial services company tasks its IT security team with reducing the network's attack surface. They have segmented the network into security zones, put port security measures in place, and physically isolated critical servers. The IT security team wants to further reduce the risk of attack by managing traffic flow between security zones. Which of the following measures should the team implement?

A$.$Use a flat or star network topology to reduce the attack surface.

B$.$Implement media access control filtering on all switch ports.

C$.$Establish an air$-$gapped network for all company servers.

D$.$Apply the principle of least privilege when defining traffic policies between zones.