Appendix D is a section typically found in reports, research papers, or books that provides supplementary information. This appendix may include additional data, charts, or detailed explanations that support the main content but are too lengthy to include in the main body. The purpose of Appendix D is to enhance the reader's understanding without interrupting the flow of the primary text. It allows authors to present relevant information that can be referenced as needed, ensuring clarity and comprehensiveness in the overall document.