Explanation:

- A nice decoration: This statement is unrelated to the idiom "a square deal." It refers to something visually pleasing or decorative.

- A dishonest transaction: This option implies deceit or trickery in an exchange, which is the opposite of what the idiom conveys.

- A fair agreement: This is the correct meaning of "a square deal." It refers to an arrangement or transaction that is just and equitable for all parties involved.

- An unfair agreement: This denotes inequity or injustice, contrary to the idiom's intended positive connotation.

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