Hi Line,
Please copy the below css in the header of the required question.
<style>
.clickable.response_row:nth-child(5) .checkbox
{
background: url("[%GraphicsPath()%]radiobutton_unselected.png") no-repeat center center !important;
}
.clickable.response_row:nth-child(5) .checkboxselected
{
background: url("[%GraphicsPath()%]radiobutton_selected.png") no-repeat center center !important;
}
</style>
where radiobutton_selected.png is the selected radio button image and radiobutton_unselected.png is the unselected radio button image, both images to be kept in the graphics folder.
Also, change 5 in child(5) with the option number of exclusive response.
Thanks,
Rahul Mittal