Buyer beware: if you're buying this book new at top dollar so you won't have to pay a separate $65 fee for the CENTRO system -- and chances are good that you are, since CENTRO allows a would-be language teacher to "call in" their class with no effort or grading at all -- prepare to be disappointed. For some reason, this brand-new book at $120 from Amazon comes keyless, even though the exact same book at your college bookstore contains one. So, there's absolutely no reason to buy one here, unless you get it used at a great price. Very, very disappointing, and just another example of college textbook publishers and book sellers ripping the public off, but at least you can learn from my mistake.