What is the correct portion marking for a contact information paragraph in a derivative document?

The correct portion marking for a contact information paragraph in a derivative document is "Unclassified." This marking indicates that the information contained in that section does not require any classification level and is suitable for public access.

In derivative classification, the need for consistent and clear communication about the sensitivity of information is essential. Contact information typically includes details such as names, phone numbers, and email addresses, which are generally not sensitive and do not pose a risk to national security if disclosed. Therefore, marking it as "Unclassified" allows anyone who reads the document to understand that this information can be shared without any restrictions.

The other options—Secret, Confidential, and Top Secret—are classifications reserved for information that could cause harm to national security if disclosed. Since contact information does not fit these criteria, those markings would be inappropriate and misleading for that type of content.