<ol>
<li>The Empire State Building, the Sears Tower, the Canadian National Tower(EACH OF THESE STRUCTURES) (WAS) the (TALLEST) in the world at the time (THEY WERE) built. (NO ERROR)</li>
</ol>
<p>thanks be nice if you guys could explain too.</p>
<p>(D)</p>
<p>Each is singular the sentence needs to be</p>
<p>The empire state building, the Sears Tower…the tallest in the world at the time it was built.</p>
<p>^
D</p>
<p>Each was built.</p>