序言

The sentence talks about a part of a book being well-written. '序言' (preface) is a suitable part of a book that can be written well. '后面' (back/behind), '中间' (middle), and '前面' (front) are general directional terms and don't fit the context as well as '序言'.

The sentence asks to read something first in a book. The '序言' (preface) is usually at the beginning and provides an introduction, making it a common thing to read first. '内容' (content) is too broad, '名字' (name) refers to the title, and '作者' (author) refers to the writer, none of which fit the 'read first' context as well as '序言'.

The sentence states that 'he introduced himself in the book's ___'. The '序言' (preface) is a common place for an author to introduce themselves or the book's purpose. '封面' (cover), '后面' (back), and '页码' (page number) are not places where someone would introduce themselves.

The sentence describes something about the book as 'short'. The '序言' (preface) can be of varying lengths, so it makes sense for it to be described as short. '价格' (price), '纸张' (paper), and '颜色' (color) are not typically described as 'short' in this context.

The sentence expresses a liking for reading a specific part of a storybook. While '结局' (ending), '插图' (illustration), and '章节' (chapter) are parts of a book, the '序言' (preface) often sets the tone or gives background, which some readers enjoy. At A2, '序言' fits a simple sentence about reading parts of a book.

The sentence says 'This dictionary has no ___'. While '笔' (pen), '字' (character), and '图片' (picture) might be related to books or dictionaries, a '序言' (preface) is a common component that a dictionary might or might not have. It's a plausible omission. Dictionaries always have '字' (characters), so that's not correct.