Unit 13 - I was doing - past continuous (Essential Grammar in Use video test)

Essential Grammar in Use
The book has been widely used by English language students, especially those from non-English-speaking countries, as a practice and reference book. The book has achieved a great reader acceptance because of its accuracy and simplicity.[citation needed] Though the book was titled as a self-study reference, the publisher states that the book is also suitable for reinforcement work in the classroom. There are three versions of the book (with answer key or without answer key or with answer key, eBook and audio). The book is divided into units, each unit (typically of two facing pages) has the lesson itself on the left page, while the right page contains exercises on that lesson. The book's units are ordered according to the lesson simplicity, or starts with the basic topics and goes up to more advanced topics. The author advises readers to flip over and find whichever topics they feel they need improvement on. A study guide is placed at the end of the book, which contains exercises that when solved reveal what topics student needs improvement on, and suggests the unit numbers the student should study; and thus the reader can figure out which units to study and which to omit.
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