<u>Answer:</u>
The part of a book that gives the author’s purpose in writing the book and acknowledges assistance from others is called the preface.
<u>Explanation:</u>
- The preface is an attempt to make the reader aware of the essence of the book broadly by giving an idea of what the writers thoughts are.
- There can be either one or two prefaces to a book, out of which, one is written by the author of the book himself. Through this preface, the author exercises the opportunity to give the people the righteous credit for the assistance provided by them in writing the book.
The word or phrase to fill into the gap is the "Ku Klux Klan", an extreme right organization calling for what they would call a "purification" of the US-American society.
