``` <div class="dropup"> <button class="btn btn-default dropdown-toggle" data-toggle="dropdown">手机品牌 <span class="caret"></span></button> <ul class="dropdown-menu"> <li class="dropdown-header">国产手机</li> <li><a href="#">小米</a></li> <li><a href="#">华为</a></li> <li><a href="#">vivio</a></li> <li class="divider"></li> <li class="dropdown-header">外国品牌</li> <li><a href="#">苹果</a></li> </ul> </div> ```