Part 2 Solution The "function listitem" work improperly..

var point = 0;
var correctAnswer = [];
var wrongAnswer = [];
var question = [
  ["This is question 1","a1"],
  ["This is question 2","a2"],
  ["This is question 3","a3"]
]; 

function listitem(arr) {
  for (var i = 0 ; i < arr.length ; i += 1) {
    var listli = "<li>" + arr[i] + "</li>";
  };
  var listul = "<ul>" + listli + "</ul>";
  return listul;
};

for (var i = 0 ; i < question.length; i +=1) { 
  if (prompt (question[i][0]) === question[i][1]) {
    point += 1;
    correctAnswer.unshift(question[i][0]);    
  } else {
    wrongAnswer.unshift(question[i][0]);
  }
};

var html = "<h2>you got " + point + " question (s) right </h2>";
html += "<strong>Correct answer</strong>";
html += listitem(correctAnswer);
html += "<strong>Wrong answer</strong>";
html += listitem(wrongAnswer);

document.getElementsByClassName("text")[0].innerHTML = html;