Transport mode is established when the enpoint is a host. If the gateway in a gateway-to-host communication was to use transport mode, it would act as a host system, which is acceptable for direct protocols to that gateway. Otherwise, TUNNEL mode is required for gateway services... This is the most common mode of operation and is required for gateway-togateway and host-to-gateway communications. Source: TIPTON, Harold F. & KRAUSE, MICKI, Information Security Management Handbook, 4th Edition, Volume 2, 2001, CRC Press, NY, page 167.

The initial security categorization for the information and the information system should be done during the initiation phase of the system development life cycle along with an initial risk assessment. The initial risk assessment defines the threat environment in which the information system will operate and includes an initial description of the basic security needs of the system.

The other options are the three principles of integrity. Answer "Prevention of authorized modifications by unauthorized users" is a distracter and does not make sensE.
* Internal consistency ensures that internal data correlate. For example, the total number of a particular data item in the database should be the sum of all the individual, non-identical occurrences of that data item in the database. External consistency requires that the database content be consistent with the real world items that it represents.

It is important to note that mandatory controls are prohibitive (i.e., all that is not expressly permitted is forbidden), not permissive. Only within that context do discretionary controls operate, prohibiting still more access with the same exclusionary principle. In this type of control system decisions are based on privilege (clearance) of subject (user) and sensitivity (classification) of object (file). It requires labeling.

Explanation/Reference:
Explanation:
Shielding is used to protect against electromagnetic emanation by reducing the size and strength of the propagated field. This makes shielding an effective method for decreasing or eliminating the interference and crosstalk. White noise is also used to protect against electromagnetic emanation. It achieves this by drowning out the small signal emanations that could normally be identified and used by unauthorized users to steal data.
Incorrect Answers:
B: Shielding and white noise are not countermeasures to Social Engineering.
C: To protect against object reuse issues, you should wipe data from the subject media before reuse.
D: Shielding and white noise are not countermeasures to Wiretapping.
References:
Miller, David R, CISSP Training Kit, O'Reilly Media, 2013, Sebastopol, pp. 261, 262, 689
https://en.wikipedia.org/wiki/Social_engineering_(security)
http://people.howstuffworks.com/wiretapping.htm