preface

这本书的前言解释了作者的写作动机。

The ___preface of this book explains the author's motivation for writing it.

作者在序言中简要介绍了本书的创作背景。

The author included a short ___preface explaining the background of this book.

这本书的序言详细介绍了作者的研究方法和目的。

The ___preface of this book outlines the author's research methods and objectives in detail.