uncheck / deselect option for scale items in Google Forms

Based on a spreadsheet (with the help of an Apps Script) I create a Google Form. Among others, the form includes Scale questions:

Is it possible for respondents to be able to somehow deselect / uncheck questions?

In case respondents are not sure anymore whether they can give a reliable answer, we want them to be able to show that. Ideally they would have the possibility to uncheck/deselect the radiobuttons again. One (not so nice) workardound would be to provide a separate "checkbox" with a label named "Unknown/Unsure". And if they are not sure they can check this checkbox. But isnt't there a better solution?

Thanks and best, Peter