Riddle quizzes run inside an iFrame. This is usually a great solution as it protects the rest of your website from anything that is going on inside the iFrame.
But if you want to maximize your page impressions for ads, it helps to refresh the ad unit, whenever someone moves to the next page in your quiz.
You can do this with a little bit of JavaScript magic.
The quiz below is a great example, refreshing the ad unit on this page.