Answer – A, purpose.
During the prewriting stage, an author will determine the purpose. This includes knowing what you are writing about and what you are writing about the specifics. When you think about writing a book, the first thing would be to ask yourself the question “why”. Why do you want to write this book and what do you want to write about? Knowing why is as important as knowing what you want to write about as this would make it easier for you to proceed with the next stage of writing.