The grammar reference and practice book used by millions of learners around the worldSimple explanations, clear examples, and easy-to-understand exercises make this book perfect for use in the classroom, or by students who are studying on their own.- Test yourself and find out your strengths and weaknesses with a simple Study Guide.- Read about the grammar and then practice, with explanations on the left-hand page and practice exercises on the right.- Improve your understanding with even more exercises in the back of the book.- Use the answer key to check your answers.With answers.Fourth Edition.