Any way I can optimize my code? Or any way I can make it clearer?

var questionAnswer = [
  ['Which planet is the closest to the Sun?', 'mercury'],
  ['What\'s the best coding language?', 'javascript'],
  ['What\'s the name of fourth farthest planet from the Sun', 'mars']  
];
var answerCorrect = 0;
var answerWrong = questionAnswer.length; 

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

for( var i = 0; i < questionAnswer.length; i += 1) {
userAnswer = prompt(questionAnswer[i][0]); 
    if ( userAnswer.toLowerCase() === questionAnswer[i][1]) {
         answerCorrect += 1;
         answerWrong -= 1; 
   }
}

var results = "<p> You answered " + answerCorrect + " correctly and " + answerWrong + " incorrectly.</p>"; 

print(results);