bootstrap class hover code example

Example 1: css hover

.a:hover{background-color: black;}

Example 2: bootstrap 4 class for hover

<div class="view overlay">
    <img src="https://mdbootstrap.com/img/Photos/Horizontal/City/6-col/img%20(3).jpg" class="img-fluid " alt="">
     <div class="mask rgba-red-strong">

    </div>
</div>