要将阴影添加到Bootstrap中的元素，请使用Bootstrap 4中的.shadow类。
您可以尝试运行以下代码以将阴影添加到元素-
<!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>