Add a custom field to a quiz
There are probably many ways doing this. I'm still new as well, so go easy on me.

I would suggest you to create a taxonomy quiz. Each list item of quiz would be your question. Then for the content type answer, have a field named question and select term reference, choose select list as the widget type. That way, when a user create a new content answer and refer to one of the question from taxonomy quiz, you can just click on the question and it will give you a list of answer.

Other ways would be using Node Reference, but I couldn't get my mind around how to refer back to the question itself, maybe Relation would do the trick.

But try my first suggestion first.