Which document provides visual guidance for marking classified national security information?

The correct response pertains to Executive Order 13526, which establishes the framework for classifying national security information. This executive order, along with the Information Security Oversight Office (ISOO) and relevant sections of the Code of Federal Regulations (CFR), provides comprehensive guidance on the classification process and includes visual aids meant to assist agencies and personnel in properly marking classified documents.

Visual guidance is particularly important for ensuring consistency and compliance within federal agencies, so that classified information is easily identifiable. The provisions outlined in the executive order and subsequent regulations detail the criteria for classification, the responsibilities of officials, and the appropriate manner in which classified information must be marked and handled, making it clear to users how to follow these protocols effectively.

The other options, while they may contain relevant information or policies, do not specifically focus on the provision of visual guidance for marking classified information as comprehensively as the combination of EO 13526 and ISOO. Therefore, the executive order and its associated regulations are recognized as the primary source for guidelines regarding the marking of classified national security information.