使用CSS：nth-child(n)选择器来设置每个<p>元素的样式，这些元素是使用CSS父元素的第二个子元素。您可以尝试运行以下代码来实现：nth-child(n)选择器
<!DOCTYPE html>
<html>
<head>
<style>
p:nth-child(4) {
background: orange;
color: white;
}
</style>
</head>
<body>
<p>This is demo text 1.</p>
<p>This is demo text 2.</p>
<p>This is demo text 3.</p>
<p>This is demo text 4.</p>
<p>This is demo text 5.</p>
<p>This is demo text 6.</p>
</body>
</html>