对Bootstrap 4卡设置否定操作
要对Bootstrap卡设置否定操作，请使用bg-warning类和该卡类，如以下示例所示-
<div class="card bg-warning"> <div class="card-body">Over 20 students failed the final-year exam.</div> </div>
让我们看一个示例，以对Bootstrap4中的卡设置负面操作-
示例
<!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 rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.0/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/4.1.0/js/bootstrap.min.js"></script>
</head>
<body>
<div class="container">
<h3>Result</h3>
<div class="card bg-warning">
<div class="card-body">Over 20 students failed the final-year exam.</div>
</div>
</div>
</body>
</html>