Interchange Third edition is a four-level series for adult and young-adult learners of English from the beginning to the high-intermediate level. The Intro Level Student's Book is designed for beginning students needing a thorough, slow-paced presentation of basic functions, grammar structures, and vocabulary. Intro is based on the principle that low-level learning does not equal low-level thinking. The Student's Book contains 16 teaching units, frequent progress checks that allow students to assess and monitor their own learning, and a self-study section. Included is a Student Audio CD that contains the conversation, pronunciation, and self-study sections from the Student's Book. Student's Book B contains units 9–16, the second half of the complete Intro Student's Book.