Use the CSS :only-of-type selector to style every <p> element that is the only <p> element of its parent.
Example
You can try to run the following code to implement the :only-of-type selector:
<!DOCTYPE html>
<html>
<head>
<style>
p:only-of-type {
background: orange;
color: white;
}
</style>
</head>
<body>
<div>
<p>This is demo text 1.</p>
</div>
<div>
<p>This is demo text 2.</p>
<p>This is demo text 3.</p>
<p>This is demo text 4.</p>
</div>
</body>
</html>