如何在此代码中打开bootstrap模式？

Question

请帮助我的twitter bootstrap模式。我似乎无法打开它。通过点击＆＃34;登录＆＃34;以及＃34;但我似乎无法正确实施它。这是代码：

<nav class ="navbar navbar-default navbar-fixed-top">
    <div class ="container-fluid">
        <div class ="navbar-header">
            <a class="navbar-brand" href="#"><span class="glyphicon glyphicon-home"></span> </a>
        </div>
        <ul class = "nav nav-pills pull-left">
            <li><a href ="#"> Create a Project </a></li>
            <li><a href ="#"> Fund a Project </a></li>
            <li><a href ="#"> Collaborate </a></li>
        </ul>
        <ul class ="nav nav-pills pull-right">
            <li><a href ="#"> About us </a></li>
            <li><a href="#"><span class="glyphicon glyphicon-user"></span> Sign up </a></li>
            <li><a href="#" data-toggle="modal" data-target="#login"><span class="glyphicon glyphicon-log-in"></span> Login </a></li>
        </ul>

    <!--login modal-->
        <div  class="modal fade" id="login" role="dialog">
            <div class="modal-dialog modal-lg">
                <div class="modal-content">
                    <div class="modal-header">
                        <button type="button" class="close" data-dismiss="modal">&times;</button>
                        <h4 class="modal-title"> Login</h4>
                    </div>
                    <div class="modal-body">
                        <p> Some text in the modal.</p>
                    </div>
                    <div class="modal-footer">
                         <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
                    </div>
                </div>
            </div>
        </div>

    </div>
</nav>