why is this code bringing out undefined?

// 1. Create a multidimensional array to hold quiz questions and answers

const QA= [ 
  ["what coutry is the billa villain from?", "indian"], 
  ["Totti is a football......?","player"], 
  ["what is rambo considered as?", "hero"] ]

// 2. Store the number of questions answered correctly 
let score=0; 
const correct =[]; 
const incorrect = [];

/*

Use a loop to cycle through each question
Present each question to the user
Compare the user's response to answer in the array
If the response matches the answer, the number of correctly answered questions increments by 1 */
for (let i=0; i<QA.length; i++) { 
  let question= QA[i][0]; 
  let answer= prompt(question);
    if (answer.toLowerCase()===QA[i][1]) {
      score++; 
      correct.push(question); 
      } else {
        incorrect.push(question); 
        } 
  }

// 4. Display the number of correct answers to the user

function createlist(arr) { 
  let items=''; 
  for (let i=0; i<QA.length; i++) { 
    items +=`<li> ${arr[i]}</li>`; 
    } 
    return items; 
    }

let html = ` 
    <h1> You got ${score} correct </h1> 
    <h2> The following are ones you got it right </h2> 
    <ol> ${createlist(correct)} </ol>
    <h2>The following are ones you got it wrong </h2>
    <ol> ${createlist(incorrect)} </ol>
    `;

document.querySelector('main').innerHTML=html;

// 4. Display the number of correct answers to the user

function createlist(arr) { 
  let items=''; 
  for (let i=0; i<QA.length; i++) { 
    items +=`<li> ${arr[i]}</li>`; 
    } 
    return items; 
    }

///not QA.length, use arr.length which is the length of the parameter you are passing to createlist
function createlist(arr) { 
  let items=''; 
  for (let i=0; i<arr.length; i++) { 
    items +=`<li> ${arr[i]}</li>`; 
    } 
    return items; 
    }