Webbrowser dropdown selected

I can not choose. I want to select the data in the dropdownlist at the desired value.

   <div role="combobox" id="rw_71_input" aria-owns="rw_71_listbox" class="rw-dropdown-list rw-widget">
        <div class="rw-widget-input rw-widget-picker rw-widget-container">
            <div class="rw-input rw-dropdown-list-input">Live</div>
            <span class="rw-select">
                <button role="presentational"   class="rw-btn rw-btn-select"><span aria-hidden="true" class="rw-i rw-i-caret-down"></span></button>
            </span></div>
        <div class="rw-popup-container rw-popup-transition-exited">
            <div class="rw-popup-transition">
                <div class="rw-popup"> 
                    <ul id="rw_71_listbox" class="rw-list" role="listbox">
                        <li role="option" aria-selected="true" >Super</li>
                        <li role="option" aria-selected="false" >Live</li>
                        <li role="option" aria-selected="false" >Education</li>
                        <li role="option" aria-selected="false" >Mannas</li>
                    </ul>
                </div>
            </div>
        </div>
    </div>

C#

 webBrowser1.Document.GetElementById("rw_71_listbox").Children[3].SetAttribute("selected", "selected");