Explanation/Reference:
A: Your inner perimeter consists of the doors, windows and walls of your building(s). Protecting your inner perimeter is usually accomplished with locks, keys and alarm systems.
D:
E: Defense in depth is a security strategy in which multiple, independent, and mutually reinforcing security controls are leveraged to secure an IT environment. Defense in depth should be applied so that a combination of firewalls, intrusion detection and prevention, user management, authentication, authorization, and encryption mechanisms are employed across tiers and network zones.
Defense in depth is compatible with perimeter security in that network perimeters (or more generically, protection zones) can make up part of the defense in depth strategy.
Incorrect answers:
B: Inner perimeter increase security.
C: Usually the perimeter or barrier itself is expanded into a third zone, named the demilitarized zone (DMZ). The DMZ offers some protection to public-facing systems, and further protection to production systems behind the perimeter firewalls.
F: Perimeter security is not effective against insider threats.
Reference: Oracle Reference Architecture, Security , Release 3.1