Radio...only one can be selected.....and if you use default then always one will pass to cart
Checkboxes....can turn them all on or all off or anywhere inbetween...so nothing could be sent to cart....
Dropdowns....solution works if you have multiple choices but only need one and not the default read-only one. But if you want more than one then that can't be done...as multiple selection in drop-downs is not in zen.....



