Which of the following is NOT an acceptable source for derivative classification?

Publicly available information is not an acceptable source for derivative classification because it does not contain information that has been officially classified by an appropriate authority. Derivative classification is the process of classifying information based on existing classified sources, and it requires that sources be officially recognized as containing classified information to ensure the integrity and security of classified material.

In contrast, classified documents, prior classified determinations, and official government reports are acceptable sources because they are based on classified information. They provide the necessary evidence or precedent from which a derivative classifier can draw conclusions about how to classify new information. Using publicly available information could lead to misunderstandings and misclassifications, as it may not account for sensitive details or contexts that lead to the classification of other materials.