Mine is slightly different and it works BUT a comma is inserted on its own line between each <li>. Why? How?

function printRight(message) {
 var pRight = document.getElementById('right');
 pRight.innerHTML= message;
}

function printWrong(message) {
 var pWrong = document.getElementById('wrong');
 pWrong.innerHTML= message;
}

var quiz = [

  ['What color is the sky?', 'blue'],
  ['What color is the grass?', 'green'],
  ['What color is ketchup?', 'red']

];


var answer;
var correct = 0;
var correctArray = [];
var incorrect = 0;
var incorrectArray = [];



for( var i = 0; i < quiz.length; i += 1) {
  answer = prompt(quiz[i][0]);
  answer = answer.toLowerCase();

   if ( answer === quiz[i][1]) {
     correct += 1;
     correctArray.push('<li>' + quiz[i][0] + '</li>');

    } else {
      incorrect += 1;
      incorrectArray.push('<li>' + quiz[i][0] + '</li>');

    }; 

};  

printRight('<h2>Total Correct: ' + correct + '</h2>' + correctArray);
printWrong('<h2>Total Incorrect: ' + incorrect + '</h2>' + incorrectArray);