You can use a Radio Buttons or Check Boxes. Radio Buttons usually require at least 2 buttons with the same name but different export values. Once one of the Radio Buttons has been selected it can only be changed by selecting other radio button. Check Boxes can be checked or unchecked. To make Check Boxes work similar to Radio Buttons, give the check boxes the same name but assign different export values to each button.
The values of Radio Buttons or Check Boxes when none of the fields in the group has been selected is "Off".