<p>(Among) the (most widespread of) marine animals, starfishes and sea urchins (inhabit) all seas (except that of) the polar regions.
The answer is “except that of” and the correct one should be “except those of”
But what about “the most widespread of”?I think we should delete “of”</p>
<p>seas–>plural noun
so “except those of” is the best answer.</p>
<p>“the most widespread of marine animals” is grammatically correct. “the most widespread” refers to the most widespread marine animals out of all marine animals. If you say “I am going to donate to the poor,” “the poor” refers to poor people. “people” is implied, so you can use the article “the” with only the adjective “poor” to refer to the poor people of society (the poor). </p>
<p>Here is the relevant definition of the word the from [url=<a href=“The]Dictionary.com[ Definition & Meaning | Dictionary.com”>The Definition & Meaning | Dictionary.com]Dictionary.com[/url</a>] (entry #7):
<a href=“used%20before%20adjectives%20that%20are%20used%20substantively,%20to%20note%20an%20individual,%20a%20class%20or%20number%20of%20individuals,%20or%20an%20abstract%20idea”>quote</a>: to visit the sick; from the sublime to the ridiculous.
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<p>Here are examples of similar usage:
The coldest of recorded 20th century winters in New York occurred in the first half. There were many cold winters in the second half of the 20th century as well, though.</p>
<p>This large dish could satisfy even the hungriest of people.</p>
<p>I am the greatest of all time.</p>
<p>Thanx! Now I understand clearly!</p>