The International Data Encryption Algorithm (IDEA) is a block cipher that operates on 64 bit blocks of data with a 128-bit key. The data blocks are divided into 16 smaller blocks and each has eight rounds of mathematical functions performed on it. It is used in the PGP encryption software.
Source: WALLHOFF, John, CBK#5 Cryptography (CISSP Study Guide), April 2002 (page
3).

Explanation/Reference:
Explanation:
A password that is the same for each log-on is called a static password. A password that changes with each log-on is termed a dynamic password. The changing of passwords can also fall between these two extremes. Passwords can be required to change monthly, quarterly, or at other intervals, depending on the criticality of the information needing protection and the password's frequency of use. Obviously, the more times a password is used, the more chance there is of it being compromised.
Incorrect Answers:
A: This answer is not complete. Passwords can also be required to change depending on the password's frequency of use.
C: This answer is not complete. Passwords can also be required to change depending on the criticality of the information needing protection.
D: Passwords CAN be required to change depending on the criticality of the information needing protection.
References:
Krutz, Ronald L. and Russell Dean Vines, The CISSP and CAP Prep Guide: Mastering CISSP and CAP, Wiley Publishing, Indianapolis, 2007, p. 57

Because the Reference Monitor is responsible for access control to the objects by the subjects it compares the security labels of a subject and an object.
According to the OIG: The reference monitor is an access control concept referring to an abstract machine that mediates all accesses to objects by subjects based on information in an access control database. The reference monitor must mediate all access, be protected from modification, be verifiable as correct, and must always be invoked. The reference monitor, in accordance with the security policy, controls the checks that are made in the access control database.
The following are incorrect:
Validation Module. A Validation Module is typically found in application source code and is used to validate data being inputted. Clearance Check. Is a distractor, there is no such thing other than what someone would do when
checking if someone is authorized to access a secure facility.
Security Module. Is typically a general purpose module that prerforms a variety of security related
functions.
References:
OIG CBK, Security Architecture and Design (page 324)
AIO, 4th Edition, Security Architecture and Design, pp 328-328.
Wikipedia - http://en.wikipedia.org/wiki/Reference_monitor