I've never used Questionnaire, so I'm not familiar with the terminology, but I'm thinking that what you're calling Radio button is called "Multiple choice - single answer" in Feedback. I've attached a screen shot showing the initial question type menu, then the drop-down choices once you've selected "Multiple choice" as your question type, and sample questions of two of the three multiple choice types of questions. "Multiple choice - single answer" gives you radio buttons, one of which can be selected. "Multiple choice - multiple answers" gives you checkboxes, any number of which can be selected. I haven't used the dropdown version.