Bootstrap challenge

please help i am trying to do a registration form but on the drop down section when going into the live server the drop down option are not showing .help here is the code


                            <button type="button" class="btn btn-primary dropdown-toggle" data-toggle="dropdown">

                              Dropdown

                            </button>

                            <div class="dropdown-menu">

                              <a class="dropdown-item" href="#">Farmer</a>

                              <a class="dropdown-item" href="#">Retailer</a>

                              <a class="dropdown-item" href="#">Driver</a>

                            </div>

                          </div>```

I’m not sure, but code have to contain some more. Look for example:


<!DOCTYPE html>
<html lang="en">
  <head>
    <!-- Необходимые Мета-теги всегда на первом месте -->
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
    <meta http-equiv="x-ua-compatible" content="ie=edge">

    <!-- Bootstrap CSS -->
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.4/css/bootstrap.min.css" integrity="2hfp1SzUoho7/TsGGGDaFdsuuDL0LX2hnUp6VkX3CUQ2K4K+xjboZdsXyp4oUHZj" crossorigin="anonymous">
  </head>
  <body>

  <div class="dropdown open">
  <button class="btn btn-secondary dropdown-toggle" type="button" id="dropdownMenuButton" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
	Dropdown Example
  </button>
  <div class="dropdown-menu" aria-labelledby="dropdownMenuButton">
    <a class="dropdown-item" href="#">HTML</a>
    <a class="dropdown-item" href="#">CSS</a>
    <a class="dropdown-item" href="#">JavaScript</a>
   </div>
  </div>

    <!-- jQuery первый, затем Tether, затем Bootstrap JS. -->
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.0.0/jquery.min.js" integrity="sha384-THPy051/pYDQGanwU6poAc/hOdQxjnOEXzbT+OuUAFqNqFjL+4IGLBgCJC3ZOShY" crossorigin="anonymous"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/tether/1.2.0/js/tether.min.js" integrity="sha384-Plbmg8JY28KFelvJVai01l8WyZzrYWG825m+cZ0eDDS1f7d/js6ikvy1+X+guPIB" crossorigin="anonymous"></script>
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.4/js/bootstrap.min.js" integrity="VjEeINv9OSwtWFLAtmc4JCtEJXXBub00gtSnszmspDLCtC0I4z4nqz7rEFbIZLLU" crossorigin="anonymous"></script>
  </body>
</html>