Which of the following areas of a textbook includes supplemental materials and additional information to the text?
A. Appendix
B. Glossary
C. Bibliography
D. Index
An appendix in a textbook typically includes supplemental materials and additional information that complements the main text. It can include charts, graphs, detailed explanations, examples, or other relevant content that enhances the reader's understanding of the subject.
Therefore, the Correct Answer is A.