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.
You can also filter questions by usage to remove any questions that you have already assigned or have placed into folders.
Go to the subject guide and select a topic.
Click on Filter to display the options.
Select Used in assignment/Not used in assignment to view questions that have or have not already been assigned.
Select Saved to folders/Not saved to folders to view questions that have or have not been saved to a folder.