Flutter Error : RangeError (index): Invalid value: Not in inclusive range 0..2: 3

I'm new to flutter and I'm making a quiz app with 3 questions but I get this error after the 3rd question:

RangeError (index): Invalid value: Not in inclusive range 0..2: 3

This is my code:

import 'package:flutter/material.dart';
import './question.dart';
import './answer.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatefulWidget {
MyApp({super.key});
@override
State<MyApp> createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
var questionIndex = 0;
void AnsweredQuestion() {
setState(() {
questionIndex = questionIndex + 1;
});
}
@override
Widget build(BuildContext context) {
var questions = [
{
'questiontext': 'What is Your Favourite Food?',
'answers': ['Pizza', 'Humburger', 'Hotdog', 'Taco']
},
{
'questiontext': 'What is Your Favourite Animal?',
'answers': ['Tiger', 'Lion', 'Parrot', 'None']
},
{
'questiontext': 'What is Your Favourite Color?',
'answers': ['Black', 'Blue', 'Red', 'Green']
}
];
var a = questions[questionIndex]['answers'] as List;
return MaterialApp(
home: Scaffold(
appBar: AppBar(
title: const Center(
child: Text('Quiz App'),
),
backgroundColor: Colors.blue,
),
body: questionIndex < questions.length
? Center(
child: Column(
children: [
Question(
questions[questionIndex]['questiontext'] as String),
ElevatedButton(
onPressed: AnsweredQuestion, child: Answer(a[0])),
ElevatedButton(
onPressed: AnsweredQuestion, child: Answer(a[1])),
ElevatedButton(
onPressed: AnsweredQuestion, child: Answer(a[2])),
ElevatedButton(
onPressed: AnsweredQuestion, child: Answer(a[3])),
],
),
)
: Center(child: Text('You Finished The Quiz!')),
),
);
}
}

I tried changing the questionIndex or changing its place and I also checked other related questions to solve my problem but I could not solve it, the code works fine when replacing questions.length by 2.

Thank You For Your Help.

As per error message , it is clear that you are going out of the range . Range is from 0 to 2 and you are trying to access 3rd index so issue goes at this line which is just below of var questions

var a = questions[questionIndex]['answers'] as List;

As you haven't added condition to check about length , it is throwing error so you can replace above code with below line of code

var a = questionIndex < questions.length ? questions[questionIndex]['answers'] as List : [];