bootstrap carousel image height

i'm having some problems with the images in bootstrap v4 image carousel. If i scale down the browser width the height of image stays the same but the width of image getting smaller so the image gets very stretched out on the height.

I have been looking at similar threads here on stackoverflow and tried everything i found in the comments but it still does not work. So i decided to make a new thread about this.

Here is a codepen link https://codepen.io/anon/pen/owNyyx but i paste the code here too if you do not wish to visit codepen :)

So here is the code i have

<div id="carouselExampleIndicators" class="carousel slide" data-ride="carousel">
  <ol class="carousel-indicators">
    <li data-target="#carouselExampleIndicators" data-slide-to="0" class="active"></li>
    <li data-target="#carouselExampleIndicators" data-slide-to="1"></li>
    <li data-target="#carouselExampleIndicators" data-slide-to="2"></li>
  </ol>
  <div class="carousel-inner" role="listbox">
    <div class="carousel-item active">
      <img class="d-block img-fluid" src="images/image1.png" alt="First slide">
      <div class="carousel-caption d-none d-md-block">
        <h3>Random Title for image1</h3>
        <p>Random description1</p>
      </div>
    </div>
    <div class="carousel-item">
      <img class="d-block img-fluid" src="images/image2.png" alt="Second slide">
      <div class="carousel-caption d-none d-md-block">
        <h3>Random title for image2</h3>
        <p>Random description2</p>
      </div>
    </div>
    <div class="carousel-item">
      <img class="d-block img-fluid" src="images/image3.png" alt="Third slide">
      <div class="carousel-caption d-none d-md-block">
        <h3>Random title for image3</h3>
        <p>Random description3</p>
      </div>
    </div>
  </div>
  <a class="carousel-control-prev" href="#carouselExampleIndicators" role="button" data-slide="prev">
    <span class="carousel-control-prev-icon" aria-hidden="true"></span>
    <span class="sr-only">Previous</span>
  </a>
  <a class="carousel-control-next" href="#carouselExampleIndicators" role="button" data-slide="next">
    <span class="carousel-control-next-icon" aria-hidden="true"></span>
    <span class="sr-only">Next</span>
  </a>
</div>