If we want to select a single element on a webpage, we can give it an ID and select it with an ID selector.

Add #firstItem to select the element with the ID "firstItem".

<html>
<head>
<style>
#firstItem{
text-decoration: line-through;}
</style>
</head>
  <body>
   <ol>
    TO DO:
    <li id="firstItem">Floss</li>
    <li>Feed Cat</li>
    <li>Nap</li>
   </ol>
</body>
</html>]]>

Make sure to pick #.