Answer:
D. The story of Atlantis, told by the Greek philosopher Plato, is a tale of a righteous society that becomes wicked.
Step-by-step explanation:
Option D is the correct option which correctly uses commas to set off a nonrestrictive clause.
Nonrestrictive clause is known as a type of clause which actually gives additional or extra information about a word or group of words whose meaning is made clear in a sentence. It is usually set off with commas.
From Option D, we discover that "...told by the Greek philosopher Plato..." is the additional information given to us about the 'The story of Atlantis".
The sentence could have still made sense if it is written like:
The story of Atlantis is a tale of a righteous society that becomes wicked.
Option D is the correct answer.