Final answer:
The text elements in chapter four are best described as having boldfaced headings with main headings centered and subheadings left-justified, and hyperlinked references in electronic versions.
Step-by-step explanation:
Based on the provided information, the best description of the text elements used in chapter four is that each heading is in boldfaced font and main headings are centered, while subheadings are left-justified. This suggests a clear organizational structure to divide the content into manageable sections. These headings are used to mark the start of sections such as the conclusion, recommendation, chapter introduction, and subsections dealing with different topics within the chapter. Additionally, references to figures, tables, glossary items, citations, chapters and sections, and other supplemental material are hyperlinked within the electronic PDF document, with blue text indicating an interactive element, and include page numbers for navigation in print versions.
The headings do not specifically address vessel weight or national boating laws based on your description, hence these options are incorrect. Also, there is no information to suggest that two heading numbers and their information are missing, nor that the headings are in italics. Therefore, we can conclude that the headings are boldfaced, with main headings centered and subheadings left-justified to organize the content in a user-friendly manner both in the electronic and print formats of the document.