Radio buttons are not empty

Hi

I prepared a questionnaire with radio buttons. I expect these buttons to be empty (unchecked) when a new visitor starts the questionnaire. However the buttons are not empty.

I also tried to make one of the buttons in the button set as default button. That doesn't seem to have an affect (i.e button 1 out of a set of three buttons was chosen as default, Yet  button 2 was checked when a new visitor started the questionnaire)

Please advise

Moshe