Which of the standard classification markings appears at the beginning of a paragraph?

The correct choice is Portion marking, which is used to indicate the classification level of specific sections within a document. This marking appears at the beginning of a paragraph to inform readers of the classification level pertaining to that particular section of text. By placing the portion marking at the start of the paragraph, it helps ensure that individuals handling the document clearly understand the sensitivity of the information being presented right from the outset.

Portion markings are essential for compliance with classification guidelines, as they facilitate the proper handling and dissemination of classified material. By clearly marking sections, it also assists in differentiating between classified and unclassified portions, especially in documents containing both types of information. Without effective portion marking, there could be a risk of mishandling sensitive content.

The other options do not serve the same purpose. Header marking typically refers to classification information provided at the top of a page, while footer marking is located at the bottom. Endnote marking pertains to footnotes or references rather than the body of the text itself. Thus, these alternative markings do not fulfill the same function as portion markings in the context of indicating classification at the beginning of a paragraph.