Adding click box to quiz slide in Captivate 9

My client wants the user to open a separate document and review before answering the quiz question.  I would normally add a click box and set the action to open another project but when I go to Interactions in the menu, the option to add a click box to the quiz slide is greyed out.  Is this normal?  Has the system been programmed so that we're not able to add click boxes and buttons on quiz slides in Captivate 9?