要创建一个块元素，请使用.d-block Bootstrap 4类。
使用d-block类-
<span class="d-block bg-info"> A block </span>
要设置不同屏幕尺寸的块，请使用.d-*-block-
<span class="d-md-block bg-info"> A block for medium screen size </span>
让我们看一个例子来学习如何创建块元素-
<!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 mt-3"> <h2>Blocks</h2> <p>Resize the browser to check the effect</p> <span class="d-block bg-info"> A block </span> <span class="d-md-block bg-info"> A block for medium screen size </span> </div> </body> </html>