<!doctype html>
<html lang="en">
<head>
<!-- 必需的元标记 -->
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
<!-- Bootstrap4 CSS -->
<link rel="stylesheet" href="https://cdn.bootcss.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
<!--标题-->
<title>Hello, world!</title>
<style>
/* Make the image fully responsive */
.carousel-inner img {
width: 100%;
height: 100%;
}
.carousel-indicators li{
width: 20px;
height: 20px;
border-radius: 50%;
background: #999;
}
</style>
</head>
<body style="background-color: #000000;">
<!--Bootstrap4 轮播-->
<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.runoob.com/images/mix/img_fjords_wide.jpg">
</div>
<div class="carousel-item">
<img src="https://static.runoob.com/images/mix/img_nature_wide.jpg">
</div>
<div class="carousel-item">
<img src="https://static.runoob.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>
<!-- 可选的 JavaScript -->
<!-- jQuery 第一, Popper.js第二, Bootstrap JS第三 -->
<script src="https://cdn.bootcss.com/jquery/3.2.1/jquery.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdn.bootcss.com/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://cdn.bootcss.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
</body>
</html>