Need help , below doesn't work

 var questions = [
    ['How many states are there in United states of America',50],
    ['Any odd number',1],
    ['Any even number',2]
    ];
var correct=[];
var wrong=[];


    function print(message){
        document.write(message);
      }

      function buildList(arr){
        var listHtml ='<ol>';
        for(var i=0; i<arr.length; i=+1){
          listHtml += "<li> "+ arr[i] + " </li>";

        }
        listHtml += '</ol>';
        return listHtml;
      }

    var question;
    var answer;
    var response;
    var html;
    var correctAnswer =0;
    for(var i =0; i<questions.length;i++){
      question = questions[i][0];
      answer = questions[i][1];
      response = parseInt(prompt(question));

      if (response === answer){
        correctAnswer +=1;
        correct.push(question);
              }
           else{
             wrong.push(question);
           }
    }

    html ="You got " + correctAnswer + " questions right.";
    html += '<h2> You got these correct answer </h2>';
    html += buildList(correct);
    html += '<h2> You got these wrong answer"</h2>';
    html += buildList(wrong);
    print(html);