javascript quiz questions

var question1;
var question2;
var question3;
var question4;
var question5;
var score = 0;

question1 = prompt('Is the sea blue?');
question1 = question1.toUpperCase();

if (question1 === 'NO') {
    alert('CORRECT!');
    score += 20;
} else {
  alert('sorry! the correct answer is no.'); 
}

question2 = prompt('Can a car only use gasoline?');
question2 = question2.toUpperCase();

if (question2 === 'NO') {
    alert('CORRECT!');
    score += 20;
} else {
  alert('sorry! the correct answer is no.'); 
}

question3 = prompt('Does it rain diamonds in jupiter?');
question3 = question3.toUpperCase();

if (question3 === 'YES') {
    alert('CORRECT!');
    score += 20;
} else {
  alert('sorry! the correct answer is yes.');
}

question4 = prompt('Are dolphin mamals?');
question4 = question4.toUpperCase();

if (question4 === 'YES') {
    alert('CORRECT!');
    score += 20;
} else {
  alert('sorry! the correct answer is yes.'); 
}

question5 = prompt('Is Javascript a programming language?');
question5 = question5.toUpperCase();

if (question5 === 'YES') {
    alert('CORRECT!');
    score += 20;
} else {
  alert('sorry! the correct answer is yes.'); 
}

if (score === 100){
  alert('Your Score is ' + score);
  alert('YOU ARE AWESOME, YOU DID PERFECT');
} else if (score <= 80 && score > 60) {
  alert('Your Score is ' + score);
  alert('Not too shabby!');
} else if (score <= 60 && score > 40) {
  alert('Your Score is ' + score);
  alert('Getting there keep it up!');
} else if (score <= 40 && score > 0) {
  alert('Your Score is ' + score);
  alert('Come on, i know you can do a lot better, try again!');
} else {
  alert('Your Score is ' + score);
  alert('You must be sleeping aren\'t you?');
}