Explanation/Reference:
Explanation:
There are three general factors that are used for authentication:
Something a person knows.

Something a person has.

Something a person is.

Two-factor authentication requires two of the three factors to be part of authentication process.
Incorrect Answers:
A: RSA encryption uses integers with exactly two prime factors, but the term "two-factor authentication" is not used in that context.
B: Measuring hand geometry twice only provides one factor.
C: Single sign-on (SSO) technology allows a user to enter their credentials once to gain access to multiple systems. Two-factor authentication could be used for SSO, not the other way around.
References:
Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, pp. 162, 163, 207, 815

The correct answer is: The subject's sensitivity label must dominate the object's sensitivity label.
With a Multi-level security policy you have information that has different sensitivity labels. In order to read an object the subject's sensitivity label must be equal to or greater than that of the object. So it would be considered to dominate it, no read up.
The following answers are incorrect: The subject's sensitivity label subordinates the object's sensitivity label. Is incorrect because if the subject's sensitivity label subordinates the object's sensitivity label that would mean it is lower and the subject should not have read access to the object.
The subject's sensitivity label is subordinated by the object's sensitivity label. Is incorrect because the this would not allow for read access if the sensitivity lables were equal. So the subject's sensitivity label is not subordinated by the object's sensitivity label, the subject's label must dominate the object's label. Remember dominate means equal to or greater than where subordinate means less than.
The subject's sensitivity label is dominated by the object's sensitivity label. Is incorrect because if the object's sensitivity label dominates the subject's sensitivity label then the subject should not have access, it is the subject that must dominate the object and not the other way around. Remember dominate means equal to or greater than so this would mean that the object's sensitivity label is equal to or greater than the subject.
According to the OIG, Multi-level security is defined as a class of system-containing information with different sensitivities that simultaneously permits access by users with different security clearances and need-to-know, but prevents users from obtaining access to information for which they lack authorization. The Subject's sensitivity label must be equal to or greater than the object's sensitivity label in order for the subject to have read access to it, no read up.

It must be noted that Halon is now banned in most countries or cities.
The reason CO2 is preferred in an information center is the agent is considered a clean agent, as well as non-conductive. The agent evaporates and does not leave a residue on the equipment. CO2 can be hazardous to people so special care must be taken when implemented.
Water may be a sound solution for large physical areas such as warehouses, but it is entirely inappropriate for computer equipment. A water spray can irreparably damage hardware more quickly than encroaching smoke or heat. Gas suppression systems operate to starve the fire of oxygen. In the past, Halon was the choice for gas suppression systems; however, Halon leaves residue, depletes the ozone layer, and can injure nearby personnel.
NOTE FROM CLEMENT:
For the purpose of the exam do not go outside of the 4 choices presented. YES, it is true that there are many other choices that would be more adequate for a Data Centre. An agent such as IG-55 from Ardent would probably be a better choice than CO2, however it is
NOT in the list of choices.
You will also notice that Shon Harris and Krutz and Vines disagree on which one is the best. This is why you must do your own research to supplement the books, sometimes books could be opiniated as well. When in doubt refer to the official book and look at what is ISC2 view of the topic and which one ISC2 considers to be the best for the exam.
ISC2 recommends also the following:
Aero-K - uses an aerosol of microscopic potassium compounds in a carrier gas released from small canisters mounted on walls near the ceiling. The Aero-K generators are not pressurized until fire is detected. The Aero-K system uses multiple fire detectors and will not release until a fire is "confirmed" by two or more detectors (limiting accidental discharge). The gas is non-corrosive, so it does not damage metals or other materials. It does not harm electronic devices or media such as tape or discs. More important, Aero-K is nontoxic and does not injure personnel.
FM-200 - is a colorless, liquefied compressed gas. It is stored as a liquid and dispensed into the hazard as a colorless, electrically non-conductive vapor that is clear and does not obscure vision. It leaves no residue and has acceptable toxicity for use in occupied spaces at design concentration. FM-200 does not displace oxygen and, therefore, is safe for use in occupied spaces without fear of oxygen deprivation.
The following are incorrect choices:
Water or Soda/Acid & Halon: (old water extinguishers) will damage sensitive equipment as well as conduct electricity which could endanger the life of the person using such a fire extinghisher. Halon has been banned due to the Montreal Protocol.
ABC rated Dry chemical extinguishers: They are suitable for electrically energized fires, but they are not acceptable on sensitive equipment. It is like throwing a couple kilograms of flour in around in a room. It is extremely hard to clean off of equipment and some of the chemicals are corrosive in nature.
Reference(s) used for this question:
Hernandez CISSP, Steven (2012-12-21). Official (ISC)2 Guide to the CISSP CBK, Third
Edition ((ISC)2 Press) (Kindle Locations 25609-25612). Auerbach Publications. Kindle
Edition.
and
http://www.ehs.ucf.edu/labsafe/safemgequip.html
or
http://www.osha.gov/doc/outreachtraining/htmlfiles/extmark.html

Guards can use discriminating judgment.
Guards are typically more expensive than automated controls, need
training as to the protection requirements of the specific site, and need to be screened and bonded.

Authentication is the act of validating a user with a unique and specific identifier.
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