我不明白为什么它不起作用。 addEventListener 未激活

一切正常，但当我单击按钮时，网站会发送给我（在启动之前）

代码不是我写的，但我的朋友 3 天前离开了我，我必须在 2 天内提供一个 webapp :)。

欢迎任何帮助。

script.js:112 Uncaught TypeError: Cannot read properties of undefined (reading 'addEventListener')
    at script.js:112:9

然后当我单击按钮时

script.js:54 Uncaught TypeError: Cannot set properties of undefined (setting 'innerHTML')
    at affectation_valeur (script.js:54:19)
    at HTMLButtonElement.init (script.js:65:1)

<!-- the questions -->
let questions = [
    {
        question: 'Quelle est la capitale de la France?',

        answers:[
            { text : 'bxl', correct:'false', index:1 },
            { text : 'juin', correct:'false', index:2 },
            { text : 'ab', correct:'false', index:3 },
      e      { text : 'paris', correct:'correct', index:4 }
        ]
    },

    {
        question: 'Quell est la capitale de la France?',

        answers:[
            { text : 'bxl', correct:'false', index:1 },
            { text : 'juin', correct:'false', index:2 },
            { text : 'ab', correct:'false', index:3 },
            { text : 'paris', correct:'correct', index:4 }
        ]
    }

]



let controls = document.querySelector('.controls');
let start = document.querySelector('#start-btn');
let next = document.querySelector('#next-btn');

let answerButtons = document.querySelector('#answer-buttons');
let btns = document.querySelector('.btn');

let container = document.querySelector('.container');
let questionContainer = document.querySelector('#question-container');
let question = document.querySelector('#question');

let i=0;
let k;
let kl;

let bodyStyle = document.body.style;
container.style.backgroundColor = '#123';

function color_int() {
    bodyStyle.backgroundColor = '#555';
    btns[0].style.backgroundColor='#f00';
    btns[1].style.backgroundColor='#ff0';
    btns[2].style.backgroundColor='#0f0';
    btns[3].style.backgroundColor='#00f';
}

function affectation_valeur(){
btns[0].innerHTML = questions[i].answers[0].text;
btns[1].innerHTML = questions[i].answers[1].text;
btns[2].innerHTML = questions[i].answers[2].text;
btns[3].innerHTML = questions[i].answers[3].text;
}

let init = function() {
questionContainer.style.display = 'block';
start.style.display = 'none';

question.innerHTML = questions[0].question;
affectation_valeur();
color_int();

}



let Reponse = function(e) {
    for (let l = 0; l<=3;l++) { if (questions[i].answers[l].correct == 'true') {x=l;}}
    for (k=0; k<=3; k++){
        if (questions[i].answers[k].correct == 'true'&& questions[i].answers[k].text == e.target.textContent){
            bodyStyle.backgroundColor = '#0f0';
            btns[k].textContent = 'Good';
        }
        
        if (questions[i].answers[k].correct == 'false'&& questions[i].answers[k].text == e.target.textContent){
            bodyStyle.backgroundColor = 'red';
            btns[k].textContent = 'bad';
        }
        if (k!=x){
            btns[k].style.backgroundColor = 'red';
            btns[k].textContent = 'bad';
        }else{
            btns[k].style.backgroundColor = '#0f0';
            btns[k].textContent = 'good';
        }
    
    }   
    kl = e.target.textContent 
}



let suivant = function(){
    i++;
    if (!kl) {alert('Choissisez une réponse avant de continuer');}
    question.innerHTML = questions[i].question;

    affectation_valeur();
    color_int();
    if(i>4){i=4}
    kl = null;
}

start.addEventListener('click', init, false);
next.addEventListener('click', suivant, false);

btns[0].addEventListener('click', Reponse, false);
btns[1].addEventListener('click', Reponse, false);
btns[2].addEventListener('click', Reponse, false);
btns[3].addEventListener('click', Reponse, false);