What layer of network defense-in-depth strategy is he trying to follow?

Damian is the chief security officer of Enigma Electronics. To block intruders and prevent any environmental accidents, he needs to set a two-factor authenticated keypad lock at the entrance, rig a fire suppression system, and link any video cameras at various corridors to view the feeds in the surveillance room.

What layer of network defense-in-depth strategy is he trying to follow?
A . Physical
B. Perimeter
C. Policies and procedures
D. Host

Answer: A