Final answer:
The content of Appendix H can vary by the textbook or resource and would likely contain supplementary material related to topics in social studies or science.
Step-by-step explanation:
The question 'Appendix H covers what 600-55' doesn't provide a clear context since different textbooks or articles can label their appendices differently. However, the information provided suggests that the student is referencing a type of textbook or educational resource. Since the provided appendices (A, B, C, etc.) contain topics such as Units, Conversion Factors, Fundamental Constants, Astronomical Data, Chemistry, and World History, it's likely that Appendix H might contain additional supplementary material relevant to these subject areas. If this is in relation to a specific textbook used within a social studies or science curriculum, you may find Appendix H to include similar supplementary material to aid in the understanding of the main content. To get an accurate answer to what Appendix H covers, you would need to reference the table of contents or index of your specific textbook.