Why are my correct answers still being marked wrong?

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

var questions = [
  ["Who is Bens favorite CEO?","ELON MUSK"],
  ["Why is 6 afraid of 7?","7 ate 9"],
  ["Is Ben smart?","YES"],
];

var rightAnswer = "";
var wrongAnswer = "";  

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

  if(answer[0].toUpperCase === questions[i][1]) {
    rightAnswer += questionNum +  questions[i][0] + "Your Answer = " + answer + ". Great Job!";
  } else {
    wrongAnswer += questionNum + questions[i][0] +
    "Your Answer = " + answer + "Correct Answer = " + questions[i][1];
  }
}

print("<h2><b>Questions Answered Correctly</b></h2>" + rightAnswer );
print("<h2><b>Questions Answered Incorrectly</b></h2>" + wrongAnswer);