Select the correct NATO portion marking for information containing NATO confidential information in the U.S. document?

The correct NATO portion marking for information containing NATO Confidential information in a U.S. document is "NATO CONFIDENTIAL." This marking should be prominently displayed at the top and bottom of the document, as well as on each page where the classified information appears. Additionally, any portion of the document that contains NATO Confidential information should be marked to indicate its classification level.