bootstract插件导航条中的下拉菜单无法显示和汉堡按钮不起作用的问题

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            <li><a href="#">Link</a></li>
            <li class="dropdown">
                <a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false">Dropdown <span class="caret"></span></a>
                <ul class="dropdown-menu">
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                    <li role="separator" class="divider"></li>
                    <li><a href="#">Separated link</a></li>
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                <ul class="dropdown-menu">
                    <li><a href="#">Action</a></li>
                    <li><a href="#">Another action</a></li>
                    <li><a href="#">Something else here</a></li>
                    <li role="separator" class="divider"></li>
                    <li><a href="#">Separated link</a></li>
                </ul>
            </li>
        </ul>
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bootstract的导航条原代码，在bootstract的网页上操作没任何问题，拷贝下来后下拉菜单无法显示，汉堡按钮也不起作用，求帮忙看下问题在哪

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这是完整的代码