How to put "RadioButton" or any kind of menu item list inside an "ExpansionPanelList"?

I am looking to create something like the following pic:

But it seems there is no proper example or tutorial on the internet, so I ask here.

I have the following code for simple ExpansionPanelList:

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        // Remove the debug banner
        debugShowCheckedModeBanner: false,
        title: 'Epnasion Radio',
        theme: ThemeData(
          primarySwatch: Colors.indigo,
        ),
        home: const HomePage());
  }
}

class HomePage extends StatefulWidget {
  const HomePage({Key? key}) : super(key: key);

  @override
  State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  // Generating some dummy data
  final List<Map<String, dynamic>> _items = List.generate(
      20,
      (index) => {
            'id': index,
            'title': 'Item $index',
            'description':
                'This is the description of the item $index. There is nothing important here. In fact, it is meaningless.',
            'isExpanded': false
          });

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Expansion List'),
      ),
      body: SingleChildScrollView(
        child: ExpansionPanelList(
          elevation: 3,
          // Controlling the expansion behavior
          expansionCallback: (index, isExpanded) {
            setState(() {
              _items[index]['isExpanded'] = !isExpanded;
            });
          },
          animationDuration: const Duration(milliseconds: 600),
          children: _items
              .map(
                (item) => ExpansionPanel(
                  canTapOnHeader: true,
                  backgroundColor:
                      item['isExpanded'] == true ? Colors.grey : Colors.white,
                  headerBuilder: (_, isExpanded) => Container(
                      padding: const EdgeInsets.symmetric(
                          vertical: 15, horizontal: 30),
                      child: Text(
                        item['title'],
                        style: const TextStyle(fontSize: 20),
                      )),
                  body: Container(
                    padding: const EdgeInsets.symmetric(
                        vertical: 15, horizontal: 30),
                    child: Text(item['description']),
                  ),
                  isExpanded: item['isExpanded'],
                ),
              )
              .toList(),
        ),
      ),
    );
  }
}

This should work for you

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}





class MyHomePage extends StatefulWidget {
  final String title;

  const MyHomePage({
    Key? key,
    required this.title,
  }) : super(key: key);

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  
  List<String> chapterAAnswers = ["A","B"];
  List<String> chapterBAnswers = ["A","B","C","D"];

  late String selectedAnswerChapterA;
  late String selectedAnswerChapterB;
  
  @override
  void initState() {
    selectedAnswerChapterA = chapterAAnswers[0];
    selectedAnswerChapterB = chapterBAnswers[0];
    super.initState();
  }
 
 
  @override
  Widget build(BuildContext context) {
    
    
    
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body:   Column(
      children: <Widget>[
         ExpansionTile(
          title: Text('Chapter A'),
         
          children: <Widget>[
             RadioListTile<String>(
          title: const Text('A'),
          value: chapterAAnswers[0],
          groupValue: selectedAnswerChapterA,
          onChanged: (String? value) {
            setState(() {
              selectedAnswerChapterA = value!;
            });
          },
        ),
        RadioListTile<String>(
          title: const Text('B'),
          value: chapterAAnswers[1],
          groupValue: selectedAnswerChapterA,
          onChanged: (String? value) {
            setState(() {
              selectedAnswerChapterA = value!;
            });
          },
        ),
          ],
        ),
           ExpansionTile(
          title: Text('Chapter B'),
         
          children: <Widget>[
             RadioListTile<String>(
          title: const Text('A'),
          value: chapterBAnswers[0],
          groupValue: selectedAnswerChapterB,
          onChanged: (String? value) {
            setState(() {
              selectedAnswerChapterB = value!;
            });
          },
        ),
        RadioListTile<String>(
          title: const Text('B'),
          value: chapterBAnswers[1],
          groupValue: selectedAnswerChapterB,
          onChanged: (String? value) {
            setState(() {
              selectedAnswerChapterB = value!;
            });
          },
        ),
             RadioListTile<String>(
          title: const Text('C'),
          value: chapterBAnswers[2],
          groupValue: selectedAnswerChapterB,
          onChanged: (String? value) {
            setState(() {
              selectedAnswerChapterB = value!;
            });
          },
        ),
             RadioListTile<String>(
          title: const Text('D'),
          value: chapterBAnswers[3],
          groupValue: selectedAnswerChapterB,
          onChanged: (String? value) {
            setState(() {
              selectedAnswerChapterB = value!;
            });
          },
        ),
          ],
        ),
     
      ],
        ),
    );
  }
}