If you get stuck, you can check the answers here. Keep in mind that there can be several ways to get to the same result. Therefore there might be some difference between your code and the code below but it doesn't necessarily mean that your code is wrong.
<!DOCTYPE html>
<html>
<body>
<h1>London</h1>
<p>London is the capital city of England. It is the most populous city in the United Kingdom, with a metropolitan area of over 13 million inhabitants.</p>
</body>
</html><!DOCTYPE html>
<html>
<body>
<h1>London</h1>
<hr>
<p>London is the capital city of England. It is the most populous city in the United Kingdom, with a metropolitan area of over 13 million inhabitants.</p>
</body>
</html><!DOCTYPE html>
<html>
<body>
<h1>Hello</h1>
<h2>Hello</h2>
<h3>Hello</h3>
<h4>Hello</h4>
<h5>Hello</h5>
<h6>Hello</h6>
</body>
</html><!DOCTYPE html>
<html>
<body>
<h1>This is a Heading
<p>This is a paragraph.
<p>This is a paragraph.
<p>This is a paragraph.
</body>
</html><!DOCTYPE html>
<html>
<body>
<a href="https://www.w3schools.com">Visit our HTML tutorial.</a>
</body>
</html><!DOCTYPE html>
<html>
<body>
<img src="pic_mountain.jpg" style="width:304px;height:228px;">
</body>
</html><!DOCTYPE html>
<html>
<body>
<ol>
<li>Coffee</li>
<li>Tea</li>
<li>Milk</li>
</ol>
</body>
</html><!DOCTYPE html>
<html>
<body>
<form>
<input type="radio" name="gender" value="male"> Male
<input type="radio" name="gender" value="female"> Female
</form>
</body>
</html>