This book has so many errors a person should be very careful when using it to study. Errors range from: -questions not matching answers in the back (completely different, as if the book was revised and the question was changed, but the answer in the back was not) -Questions that have "all of the above" answers in the back, but no all of the above option in the question. -Completely wrong answers. -Typos -Answers for a given question explain an answer that is not an option in the question For reference: 15,21,22,26,41/42,61,70,74,78,80,92,120,139,146,147,168,181,189,191,192,208, and 220 have issues. My version is 2017 edition cover, however the book inside is the 2011 edition which is confusing in itself. Honestly it appears that this book has been edited multiple times and not revised appropriately each time.