代码示例：（标识：bs_utility_mb-responsive）
<!DOCTYPE html>
<html lang="en">
<head>
<title>Bootstrap Example</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link href="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/5.1.2/css/bootstrap.min.css" rel="stylesheet">
<script src="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/5.1.2/js/bootstrap.bundle.js"></script>
</head>
<body>
<div class="p-4">
<h1>下外边距 Utility</h1>
<div class="mb-0 bg-warning">Margin Bottom 0</div>
<div class="mb-1 bg-warning">Margin Bottom 1</div>
<div class="mb-2 bg-warning">Margin Bottom 2</div>
<div class="mb-3 bg-warning">Margin Bottom 3</div>
<div class="mb-4 bg-warning">Margin Bottom 4</div>
<div class="mb-5 bg-warning">Margin Bottom 5</div>
<div class="mb-auto bg-warning" style="width:150px">Margin Bottom Auto</div>
<br>
<p>响应式下外边距实用工具。请调整浏览器窗口大小以查看效果：</p>
<div class="mb-sm-5 bg-warning">在 SM 屏幕上的 Margin Bottom 5</div>
<div class="mb-md-5 bg-warning">在 MD 屏幕上的 Margin Bottom 5</div>
<div class="mb-lg-5 bg-warning">在 LG 屏幕上的 Margin Bottom 5</div>
<div class="mb-xl-5 bg-warning">在 XL 屏幕上的 Margin Bottom 5</div>
</div>
</body>
</html>
