Answer:
C. The author refers to the evil of Sodom and Gomorrah to suggest a comparison to the contemporary city of New Orleans.
Step-by-step explanation:
An allusion is a figure that is used to describe something without directly referring to it and explicitly saying what it is, but by using some different ideas, usually knowledgable to a wider audience.
That is why the author here refers to what he imagines in New Orleans as Sodom and Gomorrah. He refers to the well known Biblical story about the cities where many vile people lived who did harm and sins, so God destroyed them at the end as a punishment for their outrageous behavior.
By alluding to these Biblical places and stories, the author is trying to say us all the worst possible happenings were present to see in New Orleans, and still are, as he is still "to this day" making that mental connection.