Help with Drag and drop

Hi there. I'm working with storyline and it's great. I've been working with people who are requesting certain types of quiz's and certain functions within the quiz's. All have gone the way they should have but the only thing that has given me trouble was the drag and drop quiz. I have a lot of content that i have managed to fit into separate objects I wanted to fit into three categories, but when I place the content into one of the categories, it covers the category completely. I was wondering if there was a way that once you placed the objects into the correct box, it would disappear, leaving the box there for more content to be placed in it.