End Course with an Automatic Fail for Wrong Answers

Are these questions part of a graded quiz? If so, you could give them a point value high enough that it would be impossible for someone to pass the quiz without answering them correctly. 

Another option: if you're just having the user go through multiple questions as practice, you could have a Results slide that only scores those 3. 

• As desired, you could redesign it. In other words, it doesn't have to look like a typical Results slide. But using one lets you take advantage of built-in functionality.