Which of the following is an authorized source for derivative classification?

The correct choice is that a properly marked source document is indeed an authorized source for derivative classification. In derivative classification, the individual creating or marking a document must rely on and reference existing source documents that clearly indicate how the information is classified.

A properly marked source document provides established classification guidance, ensuring that the derivative classifier uses information that has been vetted and classified according to official policies. This is crucial to maintaining the integrity of classified information and ensuring compliance with classification rules.

While Security Classification Guides (SCGs) are also authorized sources, relying exclusively on them for classification does not fully encompass the provision of properly marked documents. Open-source information, on the other hand, is not typically considered a reliable basis for derivative classification since it may lack the necessary clearance and oversight necessary for handling classified material.

Thus, the option regarding properly marked source documents is specifically aligned with the standards required for derivative classification, making it the correct choice in this context.