The id should be unique you can not have tribute-link as an id on another element. Especially not one that comes before the element that the test is expecting it on.
<h3 for="main" id="tribute-link" name="tribute-link">Here's a time line of Dr. Borlaug's life:</h3>
<a id="tribute-link" href="https://en.wikipedia.org/wiki/Norman_Borlaug" target="_blank"> Wikipedia entry</a>
I’ve edited your code for readability. When you enter a code block into a forum post, please precede it with a separate line of three backticks and follow it with a separate line of three backticks to make it easier to read.
You can also use the “preformatted text” tool in the editor (</>) to add backticks around text.
See this post to find the backtick on your keyboard.
Note: Backticks (`) are not single quotes (').