Which organization collaborates closely with the CNSS for national security purposes?

The correct choice focuses on the Cybersecurity and Infrastructure Security Agency (CISA) because its primary mission is to protect the nation’s critical infrastructure from cyber threats and other hazards, aligning directly with the national security objectives of the Committee on National Security Systems (CNSS). CISA collaborates with various governmental and non-governmental organizations to enhance the overall cybersecurity posture of both federal and critical infrastructure systems.

The relationship between CISA and CNSS is vital, as CISA implements the CNSS's directives, policies, and standards concerning national security systems. This partnership ensures a coordinated and effective response to cybersecurity incidents, as well as the protection of sensitive information related to national security.

The other organizations listed do play important roles in national service or security, but their primary missions do not directly correlate with the specific national security focus undertaken by CISA in collaboration with the CNSS. For instance, the National Guard primarily functions in a military context, while the National Institute of Standards and Technology deals with standards and technologies across a broader scope, and the Environmental Protection Agency focuses on environmental protection rather than cybersecurity.