Explanation/Reference:
Explanation:
Guards are appropriate whenever immediate discriminating judgement is required by the security entity.
Guards are the oldest form of security surveillance. Guards still have a very important primary function in the physical security process, particularly in perimeter control. Because of a human's ability to adjust to rapidly changing conditions, to learn and alter recognizable patterns, and to respond to various conditions in the environment, a guard can make determinations that hardware or automated security devices cannot make.
Incorrect Answers:
B: The use of physical force is not the most appropriate reason to use security guards. Therefore, this answer is incorrect.
C: The operation of access control devices typically does not require the use of security guards. Most access control devices are automatic electrical and mechanical devices that unlock and lock doors as required. Therefore, this answer is incorrect.
D: Security guards are not required to detect unauthorized access. There are many systems that can detect unauthorized access such as motion sensors etc. Therefore, this answer is incorrect.
References:
Krutz, Ronald L. and Russell Dean Vines, The CISSP and CAP Prep Guide: Mastering CISSP and CAP, Wiley Publishing, Indianapolis, 2007, p. 535