MASH "SUBMIT" Button only refreshing page.

<div class="choice-bucket">
  <h4 class="highlight">Where will you abide?</h4>
    <input name="location[]" type="text">
    <input name="location[]" type="text">
    <input name="location[]">
    <input name="location[]">
  </div>

  <div class="choice-bucket">
    <h4 class="highlight">Your future career?</h4>
      <input name="profession[]">
      <input name="profession[]">
      <input name="profession[]">
      <input name="profession[]">
  </div>

 <div class="choice-bucket">
    <h4 class="highlight">What's your favorite mammal?</h4>
      <input name="pet[]">
      <input name="pet[]">
      <input name="pet[]">
      <input name="pet[]">
  </div>

function random_number(num) {  // New function called random_choice that takes one parameter, num (or a number)
    // Get a random number between 0 and a passed-in number
    var num = num || 4  // If no number passed in, default to 4
    return Math.floor(Math.random() * num); // Round the answer down (floor) of a random number between 0 and 1 and multiply it by a number. Then return a value and exit the function.
}

function mash_choice() {  // New function called mash_choice that doesn't take any parameters 
    // Since MASH is a special case, give it its own list
    var mash = ['mansion', 'apartment', 'shack', 'house'];  // The array of choices to pick from 
    var randomNum = random_number(4);  // Use the above function to get a number between 0 and 4
    return mash[randomNum];  // Return the list item the random number function just picked and exit the function 
}

function get_answer(category) { 
    // Get a random answer from the available answers in a given category
    var choices = [];  // A blank array to hold the user provided answer  
    var selector = 'input[name="' + category + '[]"]';  // Build a CSS selector for the blanks in our passed in category 
    var inputs = document.querySelectorAll(selector);  // Get all of the inputs that match our selector 
    var answer;  

    for (var i = 0; i < inputs.length; i++) {  // Begin a for loop that will run through the code. i++ = add one to the counter which is "i"
        answer = inputs[i].value;  // Get the input with the index value of the counter and get the value ie. if they typed in dog, you get back "dog" 
        if (answer !== '') {  // If answer doesn't equal a blank... !== means doesn't equal 
            choices.push(answer); //...add it to the end of the list 
        }
    }
    return choices[random_number(choices.length)];   // Pick and return a random choice choice.length = number of answers the user provided in that category 
}

function fill_in_answers(answers) {
    // Find the spans that need filled
    var home = document.querySelector('#home');  // This says make a new variable and find the HTML tag that has the ID of "home" 
    var profession = document.querySelector('#profession');
    var pet = document.querySelector('#pet');
    var location = document.querySelector('#location');

    // Fill them with the provided answers
    home.innerText = answers['mash'];
    profession.innerText = answers['profession'];
    pet.innerText = answers['pet'];
    location.innerText = answers['location'];
    home.innerHTML = answers.mash;  // Change the content of the element in the HTML doc with the id "home" to the "mash" value in answers 
    profession.innerHTML = answers.profession;  // Change the content of the element in the HTML doc with the id "career" to the "career" value in answers 
    pet.innerHTML = answers.pet;
    location.innerHTML = answers.location;
}

function handle_submission(evt) {
    evt.preventDefault();  // Stop the form from reloading the page 
    evt.stopPropagation();  // Stop the form from reloading the page

    // Build up our answers object
    var answers = {
        'mash': mash_choice(),
        'profession': get_answer('profession'),
        'pet': get_answer('pet'),
        'location': get_answer('location')
    }
    // Fill in the answers
    fill_in_answers(answers);

    var answer_div = document.querySelector('#answers');
    answer_div.classList.add('show');
}

// Find the form on the page and attach a handler for when it's submitted
var form = document.querySelector('#mash');  
form.addEventListener('submit', handle_submission);  // Anytime the form is submitted, we want to call the function handle_submission 

body {
  font-family: Helvetica, Arial;
  font-size: 17px;
  margin: 0 auto;
  max-width: 960px;
  padding: 40px 10px;
  line-height: 1.0em;
  background: #FD6A6E;
  color: #fff;
  font-weight: 300;
}

.logo{
  width: 100%;
}

.logo img {
  margin: 0 auto;
  display: block;
}

.description {
  margin: 80px auto 40px;
  text-align: center;
}

.bucket {
  width: 100%;
  margin-bottom: 40px;
  display: inline-block;
}

.choice-bucket {
  width: 33.333333%;
  float: left;
  display: inline-block;
  margin: 0;
  padding: 0;
}

.choice-bucket input {
    font-size: 18px;
    margin: 15px 4%;
    padding: 16px 0;
    width: 92%;
    color: #BB475C;
    border-radius: 6px;
    border: 0;
    outline: 0;
    text-indent: 20px;
}

.highlight {
  font-size: 18px;
  margin-left: 30px;
  opacity: .8;
  line-height: 24px;
}

#answers {
    /* opacity: 0; */
    margin: 60px 0;
    background: #fff;
    border-radius: 6px;
    color: #BB475C;
    transition: 1s linear;
}

#answers p {
  max-width: 760px;
  margin: auto;
  padding: 80px 0;
}

#answers p span {
  font-weight: bold;
}

form input[type=submit] {
    background: #B5D269;
    border: 0;
    color: #fff;
    font-size: 20px;
    padding: 1em 2em;
    cursor: pointer;
    margin: 0 auto 60px;
    display: block;
    text-align: center;
    border-radius: 6px;
    font-weight: bold;
}

.hide {
  opacity: 0;
  height: 0;
}

.show {
  opacity: 1;
  height: 100%;
}