Which of the following are considered standard markings for classified information?

The choice of banner markings, portion markings, and a classification authority block as standard markings for classified information is correct because these elements are specified in established guidelines for handling classified documents.

Banner markings are used at the top of each page to indicate the overall classification level of a document, allowing anyone handling the material to quickly assess its sensitivity. Portion markings are applied to specific sections within the document to indicate varying classification levels of different parts, which helps ensure that only the necessary portions are handled with the appropriate precautions. Finally, the classification authority block identifies the official who classified the document, providing accountability and transparency in the classification process.

These markings play a crucial role in safeguarding sensitive information, ensuring proper management, and facilitating adherence to security protocols. This protects the integrity of the information and augments overall national security efforts.