<div id="demo" class="carousel slide" data-ride="carousel">   <!-- 指示符 -->  <ul class="carousel-indicators">    <li data-target="#demo" data-slide-to="0" class="active"></li>    <li data-target="#demo" data-slide-to="1"></li>    <li data-target="#demo" data-slide-to="2"></li>  </ul>   <!-- 轮播图片 -->  <div class="carousel-inner">    <div class="carousel-item active">      <img src="https://static.kxdang.com/images/mix/img_fjords_wide.jpg">    </div>    <div class="carousel-item">      <img src="https://static.kxdang.com/images/mix/img_nature_wide.jpg">    </div>    <div class="carousel-item">      <img src="https://static.kxdang.com/images/mix/img_mountains_wide.jpg">    </div>  </div>   <!-- 左右切换按钮 -->  <a class="carousel-control-prev" href="#demo" data-slide="prev">    <span class="carousel-control-prev-icon"></span>  </a>  <a class="carousel-control-next" href="#demo" data-slide="next">    <span class="carousel-control-next-icon"></span>  </a> </div>

<div class="carousel-item">  <img src="https://static.kxdang.com/images/mix/img_fjords_wide.jpg">  <div class="carousel-caption">    <h3>第一张图片描述标题</h3>    <p>描述文字!</p>  </div></div>