Follow these steps to see if you have used a question previously:
Under the Library tab, go to the subject guide and click on the topic that you are using.
Click on the text of the question that you would like to assign.
At the bottom of the question, click the My Usage button.
The pop-up box will tell you the assignments and folders where this question is in use. Click View to be taken directly to the Assignment Data or folder editor containing that question.