Final answer:
NIST 800-53A is pivotal for assessing the efficacy of security controls in federal information systems and organizations, providing detailed procedures to support the risk assessment process. The correct response for its importance is that it lays out the procedures for security and privacy control assessments.
Step-by-step explanation:
NIST 800-53A is essential in the risk assessment process because it provides a detailed set of procedures for conducting assessments of security controls within federal information systems and organizations. Option C is the correct answer, as it directly states the publication's purpose of providing procedures for security control assessments. However, option A is also partially correct as NIST 800-53A helps in detailing how to conduct the assessment and how it fits within the broader organizational risk management processes. Option B describes the broader goal covered more by NIST 800-37 and NIST 800-39 than NIST 800-53A.
The key importance of NIST 800-53A is found in its comprehensive approach to assessing security controls, which ensures that the controls are effective and can protect the sensitive information within the federal systems. The implementation of these controls according to the guidelines helps in mitigating risks associated with operational activities, assets, individuals, and the nation at large.