Despite the many, many tutorials I have searched through, the dropdown feature of my navigation bar is not functioning. Please help if you know some sort of difference with multidimensional dropdown menus in Bootstrap 3 that I am not seeing.

```
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head>
   <meta name="generator" content=
  "HTML Tidy for Linux/x86 (vers 25 March 2009), see www.w3.org" />

  <title>Bootstrap 101 Template</title>
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <!-- Bootstrap -->
  <link href="css/bootstrap.min.css" rel="stylesheet" media="screen" type="text/css" />
  <!-- HTML5 shim and Respond.js IE8 support of HTML5 elements and media queries -->
  <!--[if lt IE 9]>
      <script src="../../assets/js/html5shiv.js"></script>
      <script src="../../assets/js/respond.min.js"></script>
    <![endif]-->
</head>

<body>
  <div class="navbar-header">
    <a class="navbar-brand" href="#">Brand</a>
  </div>

  <div class="collapse navbar-collapse navbar-ex1-collapse">
    <ul class="nav navbar-nav">
      <li class="active"><a href="#">Home</a></li>

  <li><a href="#">The Artists</a></li>

  <li><a href="#">The Art</a></li>

  <li class="dropdown">
    <a href="#" class="dropdown-toggle" data-toggle="dropdown">Schedule</a>

    <ul class="dropdown-menu">
      <li><a href="#">Day One</a></li>

      <li><a href="#">Day Two</a></li>

      <li><a href="#">Day Three</a></li>
    </ul>
  </li>

  <li><a href="#">Venue</a></li>

  <li><a href="#">Hotels</a></li>
</ul>

<ul class="nav navbar-nav navbar-right">
  <li>
    <form class="navbar-form navbar-left" role="search">
      <div class="form-group">
        <input class="form-control" type="text" placeholder="Search" />
      </div><button style="margin-left: 5px;" class="btn btn-default" type=
      "submit">Submit</button>
    </form>
  </li>
</ul>
  </div>
</body>
</html>

```