<img src="https://cdn.pixabay.com/photo/2016/08/11/23/48/mountains-1587287_1280.jpg" class="img-thumbnail" >

External CSS

  1. https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.5.0/css/bootstrap.min.css

External JavaScript

This Pen doesn't use any external JavaScript resources.