I bought this book, but I don't know how this can be helpful when there are is no answer key!  Even the CD, you take the test, but it does not tell you what is correct or incorrect!  I thought that it would give correct or incorrect answer at least on that but it does not.  It just gives you the number of points you scored.  What good is that to a someone trying to learn?

Am I missing something?  Did anyone find this helpful or find a way to check your answers or get explanations?