<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"></script>
<script src="//code.jquery.com/jquery-1.11.1.min.js"></script>
<div class="container">
<div class="row">
<div class="col-12 text-center"><h1>Responsive video</h1></div>
<div class="col py-2">
<div class="video"><iframe src="https://www.youtube.com/embed/AWdA7hdP4ZA?rel=0&showinfo=0" frameborder="0" allowfullscreen></iframe></div>
</div>
<div class="col py-2">
<div class="video"><iframe src="https://www.youtube.com/embed/I39RKjerJss?rel=0&showinfo=0" frameborder="0" allowfullscreen></iframe></div>
</div>
<div class="col py-2">
<div class="video"><iframe src="https://www.youtube.com/embed/Dkx4LYeFnVY?rel=0&showinfo=0" frameborder="0" allowfullscreen></iframe></div>
</div>
</div>
</div>