For Checklist Boxes, Multiple Choice and Drop Down response types, you must specify the possible answers to the question. In that case you will see this screen with a blue Answers button. Click on it to enter your list of acceptable responses to the question.
*For some user defined fields, you should be sure to include a “None” or 0 selection if you are requiring a response. For example, you might want to require a response to the T-shirt size question but allow players to select “None” if they do not want a t-shirt.