Each of Gleim's audio series contains 12 lectures. Normally you would be riding in a car, airplane, etc. without a computer screen in front of you. There is coverage of all questions that will appear on your pilot knowledge test. After discussion of a tested concept, the audio states "On the FAA test ..." followed by the correct answer or answers to the question or questions on that topic. Thus, when you practice answering questions AND when you take your test, you will know the correct answers.