Radial selector does not allow to unmark options leaving it blank

On showing a radial field to user, just one option shall be selected, but can not unmark a selection to leave it blank. Just change it. A double click on an option could be the solution to unmark leaving field blank.
For example if you have different languajes and want to select level, but you made a mistake, you can not mark.

I added a “No” option to solve the problem. Any other suggestion? Should it be fixed to allow unmark options?