You can remove the current answer and question with the correct answer (maybe show a message about the correct answer being picked with a delay); then, have the world check to see if they are still in the world, and if not, add a new set of answers and a new question. The world can count the number of times it finds none in the world to determine what set to show next; and also, if needed, know when to stop supplying questions (maybe print final results on a game over screen or something like that).

The thing is that i don't know the code that i should use. I can make it dissapear. But i don't know how to put the new actor in the same coordinates. And that for each answer (both correct and incorrect) and the question given after answering correctly.

Please show your world class code.