If you want to stay with the default question slides, there are a lot of limitations. The only interactive object that can be inserted on a question slide is a shape button, but even then there are some tricks to be used. You didn't tell which version you are using, and if you are talking about many MCQ? Resetting the slide to the state with the hidden shape button is a breeze, with shared actions. But those are only available in 7 and improved in 8.
Buttons on Question/Score Slides in Captivate 6? - Captivate blog just FYI, don't talk about shared actions there, only about using shape buttons on question slides.