<p>Please tell me why this is right :</p>
<ol>
<li>Henry Wadsworth Longfellow was a descendant of john and Priscilla Alden, (whose romance he celebrated) in the narrative open “The Courtship of Miles Standish.”</li>
</ol>
<p>“whose romance he celebrated” is the answer, but how come it is not run-on sentence?</p>