Which marking is correctly formatted for a document containing Secret SAP information?

The correct choice indicates a proper format for marking a document that contains Secret Special Access Program (SAP) information. In the context of classified documents, the marking used to denote the security classification must conform to specific guidelines outlined in national security directives.

For materials containing Secret SAP information, the proper marking is "SECRET//WW," which stands for “Secret” classification with “WW” denoting that this information has been safeguarded in a way that requires handling with care. This format accurately reflects the classification level and the special access needed, ensuring that individuals who encounter the document understand both its sensitivity and the requirements for its safekeeping.

Additional marks like "FW" (for "Focus Work") or designations that do not reflect the SAP designation would not provide the necessary security information for handling sensitive government material. Furthermore, "NATO SECRET//WW" pertains specifically to information designated by NATO, which does not apply to the classification of SAP information under the U.S. classification system. Therefore, this option provides the clarity and adherence to regulations expected of such a document.