Problems with Psuedo

I’m having serious problems with HTML & CSS course pseudo selectors 23. I now cannot continue with the course as it is the end of a section, so I can’t skip it. My CSS code is:

body :nth-child(4) {
font-size: 26px;

My HTML code is:

<!DOCTYPE html>
		<link type="text/css" rel="stylesheet" href="stylesheet.css"/>
		<!--Add your HTML below!-->
		<h3 class="fancy">HELLO</p>
		<p class="fancy">It's my favourite word</p>
		<p id="serious">I am serious</p>
		<p>Hello again</p>

Why do I keep getting the syntax error:

Oops, try again. Did you give your third paragraph a font-size of 26px? It looks like it’s currently undefined.

Please help!

You close your heading (h3) with a paragraph closing tag, that will mess up the count