Interchange Is A Four-level, American English Course That Has Been Used By Over 50 Million Students Worldwide. This Level 2b Student's Book With Digital Pack Has Units 9-16, Progress Checks, And A Grammar Plus Section To Ensure Students Receive All The Practice They Need. Inside Each Book Is A Single-use Code For The Digital Pack To Access The Digital Workbook With Hundreds Of Self-graded Exercises, Audio, Videos, And An . The Digital Pack Is Mobile-friendly And Can Be Used On A Smartphone, Tablet, Or Computer. Leia Mais