<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<div class="container">
<h1 class="font-weight-light text-center mt-4 mb-0">Thumbnail Gallery</h1>
<hr class="mt-2 mb-5">
<div class="row text-center ">
<div class="col-lg-3 col-md-4 col-6">
<a href="#" class="d-block mb-4 h-100">
<img class="img-fluid img-thumbnail" src="https://source.unsplash.com/pWkk7iiCoDM/400x300" alt="">
</a>
</div>
<div class="col-lg-3 col-md-4 col-6">
<a href="#" class="d-block mb-4 h-100">
<img class="img-fluid img-thumbnail" src="https://source.unsplash.com/aob0ukAYfuI/400x300" alt="">
</a>
</div>
<div class="col-lg-3 col-md-4 col-6">
<a href="#" class="d-block mb-4 h-100">
<img class="img-fluid img-thumbnail" src="https://source.unsplash.com/EUfxH-pze7s/400x300" alt="">
</a>
</div>
<div class="col-lg-3 col-md-4 col-6">
<a href="#" class="d-block mb-4 h-100">
<img class="img-fluid img-thumbnail" src="https://source.unsplash.com/M185_qYH8vg/400x300" alt="">
</a>
</div>
<div class="col-lg-3 col-md-4 col-6">
<a href="#" class="d-block mb-4 h-100">
