Matching - Drag and Drop

I'm creating a matching drag and drop exercise.  The learner will drag and drop 6 words next to their definitions and then click a submit button.  I want to show the "that is correct" layer only when the learner has dragged and dropped all the words next to their correct definitions.  I want to show the "that is incorrect" layer if the learner hasn't dragged and dropped correctly.  I'd like to give them two chances before the "correct" answers are displayed.  

My question is:

1. What triggers or variables do I need to set up in order to make this work?  

I've attached an example project for reference...