AP Calculus AB Exam Study Prep

This application is a great tool for calculus study. I use it to check what I need extra assistance for. One suggestion for this app is for a brief explanation during review, to know why you got a question wrong. This would be much use to me, since I'm sometimes left confused and don't know where to correct my work. However, I currently have one problem with it. On my phone, when advertisements appear, they block the fourth answer! When I exited and reopened the quiz, a different advertisement would pop up in the same spot. I would appreciate it if this problem were fixed.