Allow only single selection on RadioListTile options flutter

My radioListTile is allowing multiple selections instead of single selection.

class _OptionsCardState extends State<OptionsCard> {
  String? groupedValue = "";

  @override
  Widget build(BuildContext context) {
  return Card(
   color: AppColors.lightBlue,
   child: RadioListTile<String>(
    title: Text(widget.option),
    value: "{${widget.option}}",
    groupValue: groupedValue,
    onChanged: (value) => {
      setState(() {
        groupedValue = value;
      }),
      widget.onChangeSelectedInput!(value??"")
    }
   ),
  );
 }
}

I am calling like this in another screen

for(var item in _questions[index].options!) OptionsCard(
     option: item, color: Colors.black,
     onChangeSelectedInput: (String value) {
     debugPrint("selected ${value}");   <-- this is printing the selected 
     value as --> {selectedValue} with the right value I only need selectedValue without the brackets
     
     },
 )

Not sure what I am doing wrong..

In summary how to:

1. Make only one option selectable
2. Get the selected item as string instead of {string}

1. You should manage the state of selected group value in common widget(page)
2. You are having extra and unwanted {} on RadioListTile
   I made following changes to achieve this

OptionsCard

class OptionsCard extends StatelessWidget {
  const OptionsCard({Key? key, required this.option, this.groupValue, required this.onChangeSelectedInput, this.color})
      : super(key: key);
  final String option;
  final String? groupValue;
  final Color? color;
  final Function(String) onChangeSelectedInput;

  @override
  Widget build(BuildContext context) {
    return Card(
      color: AppColors.lightBlue,
      child: RadioListTile<String>(
          title: Text(option),
          value: option,//Here you have unwanted {} as '{${widget.option}}'
          groupValue: groupValue,
          onChanged: (value) => onChangeSelectedInput(value ?? "")),
    );
  }
}

PageState(Usage of OptionCard)

for (var item in _questions[index].options!)
    OptionsCard(
      option: item,
      color: Colors.black,
      groupValue: groupValues[index],
      onChangeSelectedInput: (String value) {
        debugPrint("selected ${value}");
        setState(() {
          groupValues[index] = value;
        });
      },
    )

And in the main page state, you should have a field variable groupValues

Map<int, String> groupValues = {};//Group value should be in common for all RadioButtons

If you really like to have single selection for all questions, then you should have String? groupValue; instead of groupValues