Aesop's Fables-- is there a singular form?

Open Forum
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Hello.

“The Tortoise and the Hare” is ______.
Which of the following choices do you think is grammatically correct to fill in the blank?

1 an Aesop’s Fable
2 an Aesop Fable
3 an Aesop’s fable
4 an Aesop fable

Thanks in advance.

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Referenced in separate post

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