谁能帮我看下为什么下拉菜单点不开？要吐血了

<li role="presentation" class="dropdown">
      <a class="dropdown-toggle" data-toggle="dropdown" id="dropdownMenu1" href="#">功能
    <span class="caret"></span>
   </a>
    <ul class="dropdown-menu" role="menu" aria-labelledby="dropdownMenu1">
        <li role="presentation"><a role="menuitem" tabindex="-1" href="#">Action</a></li>
        <li role="presentation"><a role="menuitem" tabindex="-1" href="#">Another action</a></li>
        <li role="presentation"><a role="menuitem" tabindex="-1" href="#">Something else here</a></li>
        <li role="presentation"><a role="menuitem" tabindex="-1" href="#">Separated link</a></li>
    </ul>
  </li>