BootStrap中<li role=

<ul>
 <li>Coffee</li>
 <li>Tea</li>
 <li>Milk</li>
</ul>

<div class="dropdown">
 <button class="btn btn-default dropdown-toggle" type="button" data-toggle="dropdown">
 选择你喜欢的品种
 <span class="caret"></span>
 </button>
 <ul class="dropdown-menu" role="menu" aria-labelledby="dropdownMenu1">
 <li role="presentation" class="dropdown-header">选择你喜欢的水果</li>
 <li role="presentation"><a role="menuitem" tabindex="-1" href="#">苹果</a></li>
 <li role="presentation"><a role="menuitem" tabindex="-1" href="#">香蕉</a></li>
 <li role="presentation"><a role="menuitem" tabindex="-1" href="#">菠萝</a></li>
 <li role="presentation" class="divider"></li>
 <li role="presentation" class="dropdown-header">选择你喜欢的树木</li>
 <li role="presentation"><a role="menuitem" tabindex="-1" href="#">松树</a></li>
 <li role="presentation"><a role="menuitem" tabindex="-1" href="#">白杨</a></li>
 <li role="presentation"><a role="menuitem" tabindex="-1" href="#">柳树</a></li>
 <li role="presentation" class="divider"></li>
 <li role="presentation" class="dropdown-header">选择你喜欢的蔬菜</li>
 <li role="presentation"><a role="menuitem" tabindex="-1" href="#">芹菜</a></li>
 <li role="presentation"><a role="menuitem" tabindex="-1" href="#">萝卜</a></li>
 <li role="presentation"><a role="menuitem" tabindex="-1" href="#">白菜</a></li>
 <li role="presentation" class="divider"></li>
 </ul>
</div>