radio represents a group of radio buttons (<input type="radio"> in HTML). Note that there is no required version of radio (“radio*”). The reason Contact Form 7 doesn’t provide “radio*” is because a radio button is a required field by nature. The HTML spec document explains it more in detail.
This isn't the case for me. Using Chrome on the http://contactform7.com/checkboxes-radio-buttons-and-menus/ demo page when you submit you can see options are not required and form can be sent without selecting any of the options. In the first instance option is are selected so no problem but once the form is sent, option becomes un selected and consecutive form send does not require options to be selected.
Additionally when I use Chrome with 'Auto-fill' function turned on my browser, once the auto fill option is selected, all the options become unselected even though they were pre selected. Then the same problem occurs when you send the form, form goes without the warning (radio button is a required field by nature) does not work.
Is this common? has anyone a solution to this?