Can't get quiz game to work

Everything was going fine. I made an object variable called "correctAnswer", and made it so that, at the start of each question, the variable sets its value to one of the answers (3D texts). I made four events for each of them, so that when a user clicks them, a method called "world.checkForCorrectAnswer" will be called. It consists of nested If/Else statements that check if the selected answer is correct. If the right answer is picked, "world.nextQuestion" should be called, but if not, the display text should say "Wrong!"

However, I cannot get this to work. I tried picking the wrong answer and saw no text. Please help! (Click below for the file)

Also NOTE that I have not finished the "Next Question" method, which is why I picked the wrong answer to test it.