What must be included in the markings of classified documents according to regulations?

The correct answer highlights the key components that must be marked on classified documents as outlined by regulations. Specifically, classified documents must include the classification level, which indicates the degree of sensitivity and the level of protection required; handling instructions, which provide guidance on how to manage the document to ensure its protection; and the identity of the classification authority, which helps to establish responsibility for the classification determination.

Including the classification level is essential for ensuring that individuals who handle the document understand the risks associated with unauthorized disclosure. Handling instructions are critical for guiding personnel in the proper management and dissemination of the information contained within the document. Lastly, identifying the classification authority aids in accountability and ensures that there is a designated person or entity responsible for the categorization of the information.

Other options, while they may contain relevant information, do not encompass the mandatory elements required for properly marking classified documents.