使用Bootstrap 4向元素添加阴影
要将阴影添加到Bootstrap中的元素，请使用Bootstrap4中的.shadow类。
您可以尝试运行以下代码以将阴影添加到元素-
示例
<!DOCTYPE html>
<html>
<head>
<title>Bootstrap Example</title>
<link rel = "stylesheet" href = "https://maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css">
<script src = "https://cdn.staticfile.org/jquery/3.3.1/jquery.min.js"></script>
<script src = "https://maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script>
</head>
<body>
<div class = "container">
<h1>Learning</h1>
<div class = "shadow-lg p-4 mb-4 bg-light">Try programming examples</div>
<div class = "shadow-sm p-4 mb-4 bg-light">Try programming examples</div>
<div class =" shadow-none p-4 mb-4 bg-light">Play Quiz and check your knowledge</div>
</div>
</body>
</html>