In the following sentence, should it be 'discuss' or 'discusses'?
This book includes three chapters, which discusses on the examples of adaptation, evolution and survival, providing a further understanding of the three processes.
In the following sentence, should it be 'discuss' or 'discusses'?
This book includes three chapters, which discusses on the examples of adaptation, evolution and survival, providing a further understanding of the three processes.
The verb discuss must agree with three chapters, so it needs the plural form, discuss. If the book contains exactly three chapters:
This book includes three chapters, which discuss the examples...
The three chapters in this book discuss...
If it contains more than three chapters, remove the comma:
This book includes three chapters which discuss the examples...
This book includes three chapters that discuss the examples...
Three chapters in this book discuss...
Note, also, that we discuss something, or we have a discussion on something, but we don't discuss on something.