Edit webinar registration questions (revise existing custom questions)

I added custom questions to a webinar registration.  Now that some registrations are coming through, I have realized that there is a mistake on the dropdown for one of my custom questions.  My only option seems to be to ADD additional questions, but I don't see an option to edit my existing question.

Number of employees needs to be edited.

Adding a new question seems to be my only option, but then it would be duplicated, since I can't find anywhere to delete the original question.