Never use a lone radio button Usability

Radio buttons are designed to be used as a group of mutually exclusive options, so always use at least two radio buttons together.

A lone radio button can be checked, but cannot be unchecked by clicking it again. If users can choose not to activate any of the radio button choices, provide a choice labeled None or use a checkbox.

References

• Radio button - Wikipedia
• Checkboxes vs. Radio Buttons - Jakob Nielsen