What Is World English？
World English is a course in the English language. It is intended for students whose native language is not English. It is a basic programme consisting of six stages. Each stage includes a Student Book, a Teacher's Book, a Workbook, and cassette recordings. World English is further supported by separate books of readings, by tests, and by visual (可视的) aids.
Who is World English for？
World English may be entered at any one of three different levels. The First Level, Books One and Two, is intended for students with little or no education in English. Books Three and Four make up the Second Level; they are suitable for students who have some knowledge of English. The Third Level, Books Five and Six, is intended for students who are concerned with improvement in the language.
What does world English teach？
World English teaches four basic skills of language: listening, speaking, reading, and writing. At all levels, each skill is presented systematically. In the First Level, listening and speaking receive more attention. In the latter books, reading and writing become more important. However, reading and writing activities are presented even in Unit One of Book One; and listening and speaking exercises occur through Unit One of Book One; and listening and speaking exercises occur though Unit Ten of Book Six.
This passage is probably taken from the ______ of an English textbook.

A. contents
B. introduction
C. first chapter
D. index (索引)