The iris pattern is considered lifelong. Unique features of the iris are: freckles, rings, rifts, pits, striations, fibers, filaments, furrows, vasculature and coronas. Voice, signature and retina patterns are more likely to change over time, thus are not as suitable for authentication over a long period of time without needing re-enrollment. Source: FERREL, Robert G, Questions and Answers for the CISSP Exam, domain 1 (derived from the Information Security Management Handbook, 4th Ed., by Tipton & Krause).

Explanation/Reference:
With Discretionary Access Control, the subject has authority, within certain limitations, to specify what objects can be accessible.
For example, access control lists can be used. This type of access control is used in local, dynamic situations where the subjects must have the discretion to specify what resources certain users are permitted to access.
When a user, within certain limitations, has the right to alter the access control to certain objects, this is termed as user-directed discretionary access control. In some instances, a hybrid approach is used, which combines the features of user-based and identity-based discretionary access control.
References:
KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 33.
and
HARRIS, Shon, All-In-One CISSP Certification Exam Guide 5th Edition, McGraw-Hill/Osborne, 2010, Chapter 4: Access Control (page 210-211).

Section: Security Operation Adimnistration
Explanation/Reference:
The CPU, storage devices and peripherals each have specialized roles in the security archecture. The CPU, or microprocessor, is the brains behind a computer system and performs calculations as it solves problemes and performs system tasks. Storage devices provide both long- and short-term stoarge of information that the CPU has either processed or may process. Peripherals (scanners, printers, modems, etc) are devices that either input datra or receive the data output by the CPU.
The motherboard is the main circuit board of a microcomputer and contains the connectors for attaching additional boards. Typically, the motherboard contains the CPU, BIOS, memory, mass storage interfaces, serial and parallel ports, expansion slots, and all the controllers required to control standard peripheral devices.
Reference(s) used for this question:
TIPTON, Harold F., The Official (ISC)2 Guide to the CISSP CBK (2007), page 308.