The correct answer is "A chapter or unit overview".
A copyright page is only concerned with legalities, and it will be of no help in your studying of the material.
An appendix often contains information related to the material at hand or other texts that could be useful for further reading, but it does not develop upon de content of the textbook.
Finally, a chapter or unit overview (as its name indicates) <u>will give you a general idea or summary of what the actual contents of the textbook are</u>. Reading this information is certain to be useful for your understanding of what the aims and topics of the material are. That's why this is the correct answer.
