<!doctype html>
<html lang="en">

<head>
    <!-- Required meta tags -->
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">

    <!-- Bootstrap CSS -->
    <link rel="stylesheet" href="<https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/css/bootstrap.min.css>"
        integrity="sha384-Vkoo8x4CGsO3+Hhxv8T/Q5PaXtkKtu6ug5TOeNV6gBiFeWPGFN9MuhOf23Q9Ifjh" crossorigin="anonymous">

    <title>Hello, world!</title>
    <style>
        .col-md-3,
        .col-md-4,
        .col-md-6{
            border: solid 1px black;
        }
    </style>
</head>

<body>
    <nav class="navbar navbar-expand-lg navbar-light bg-light">
        <a class="navbar-brand" href="#">Navbar</a>
        <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
          <span class="navbar-toggler-icon"></span>
        </button>
      
        <div class="collapse navbar-collapse" id="navbarSupportedContent">
          <ul class="navbar-nav mr-auto">
            <li class="nav-item active">
              <a class="nav-link" href="#">Home <span class="sr-only">(current)</span></a>
            </li>
            <li class="nav-item">
              <a class="nav-link" href="#">Link</a>
            </li>
            <li class="nav-item dropdown">
              <a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
                Dropdown
              </a>
              <div class="dropdown-menu" aria-labelledby="navbarDropdown">
                <a class="dropdown-item" href="#">Action</a>
                <a class="dropdown-item" href="#">Another action</a>
                <div class="dropdown-divider"></div>
                <a class="dropdown-item" href="#">Something else here</a>
              </div>
            </li>
            <li class="nav-item">
              <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
            </li>
          </ul>
          <form class="form-inline my-2 my-lg-0">
            <input class="form-control mr-sm-2" type="search" placeholder="Search" aria-label="Search">
            <button class="btn btn-outline-success my-2 my-sm-0" type="submit">Search</button>
          </form>
        </div>
      </nav>
    <!-- JavaScript -->
    <script src="<https://cdn.jsdelivr.net/npm/[email protected]/dist/js/bootstrap.bundle.min.js>"></script>
</body>

</html>