The correct answer is Key exchange. The other answers are key management issues, but key exchange is a function of the encryption system.

Public key cryptography is one mechanism that is often used to fulfill the security requirements necessary to conduct electronic transactions over public networks. PKI (public key infrastructure) and cryptography based solutions are taking the lead in secure e-commerce. PKI addresses nonrepudiation of identity using a dual-key encryption system that allows users to uniquely sign documents with a digital signature. Public key cryptography uses pairs of keys, each pair consisting of one public key and one private key. Information encrypted with one key in the pair can only be decrypted with the other key. LDAP is issued to bring user information and Timestamping to track changes over time. PKI also relies on certificated and CRL (Certificate Revocation list) to discard compromised, expired digital certificates.

The most commonly used fence is the chain linked fence and it is the most affordable. The standard is a six-foot high fence with two-inch mesh square openings. The material should consist of nine-gauge vinyl or galvanized metal. Nine-gauge is a typical fence material installed in residential areas.
Additionally, it is recommended to place barbed wire strands angled out from the top of the fence at a 45(o) angle and away from the protected area with three strands running across the top. This
will provide for a seven-foot fence. There are several variations of the use of "top guards" using V-
shaped barbed wire or the use of concertina wire as an enhancement, which has been a
replacement for more traditional three strand barbed wire "top guards."
The fence should be fastened to ridged metal posts set in concrete every six feet with additional
bracing at the corners and gate openings. The bottom of the fence should be stabilized against
intruders crawling under by attaching posts along the bottom to keep the fence from being pushed
or pulled up from the bottom. If the soil is sandy, the bottom edge of the fence should be installed
below ground level.
For maximum security design, the use of double fencing with rolls of concertina wire positioned
between the two fences is the most effective deterrent and cost-efficient method. In this design, an
intruder is required to use an extensive array of ladders and equipment to breach the fences.
Most fencing is largely a psychological deterrent and a boundary marker rather than a barrier,
because in most cases such fences can be rather easily penetrated unless added security
measures are taken to enhance the security of the fence. Sensors attached to the fence to provide
electronic monitoring of cutting or scaling the fence can be used.
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 24416-24431). Auerbach Publications. Kindle Edition.

This step is not a part of RISK ANALYSIS.
A risk analysis has three main goals: identify risks, quantify the impact of potential threats, and
provide an economic balance between the impact of the risk and the cost of the associated
countermeasure. Choosing the best countermeasure is not part of the risk analysis.
Source: HARRIS, Shon, All-In-One CISSP Certification Exam Guide, McGraw-Hill/Osborne, 2002,
chapter 3: Security Management Practices (page 73).
HARRIS, Shon, Mike Meyers' CISSP(R) Certification Passport, 2002, McGraw-Hill, page 12.

RAID Level 2 :- The parity information is created using a hamming code that detects errors and establishes which part of which drive is in error. Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 66.