In this type of control, a lattice model is applied.
To apply this concept to access control, the pair of elements is the subject and object, and the subject has to have an upper bound equal or higher than the object being accessed.
WIKIPEDIA has a great explanation as well:
In computer security, lattice-based access control (LBAC) is a complex access control based on the interaction between any combination of objects (such as resources, computers, and applications) and subjects (such as individuals, groups or organizations).
In this type of label-based mandatory access control model, a lattice is used to define the levels of security that an object may have and that a subject may have access to. The subject is only allowed to access an object if the security level of the subject is greater than or equal to that of the object.
Reference(s) used for this question:
KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten
Domains of Computer Security, 2001, John Wiley & Sons, Page 34
and
http://en.wikipedia.org/wiki/Lattice-based_access_control

Explanation/Reference:
Explanation:
The verification of message integrity is an important application of secure hashes.
Incorrect Answers:
A, D: A hash function provides Integrity, not confidentiality or authentication.
B: A hash function provides Integrity, not availability.
References:
https://en.wikipedia.org/wiki/Cryptographic_hash_function
Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, p. 825

The Domain Name System (DNS) is a global network of servers that provide these Domain
Name Services.
Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the
Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 100.

Custodian - Preserves the information's CIA (chart) -Ronald Krutz The CISSP PREP Guide (gold edition) pg 15