What must be true for an acceptance to be valid under the "mirror image rule"?

For an acceptance to be valid under the "mirror image rule," it is essential that the acceptance exactly matches the terms of the offer. This rule asserts that the acceptance must reflect the offer in every aspect without any discrepancies, ensuring that both parties are in complete agreement on the terms of the contract. This strict standard prevents any modifications or additional terms from altering the original intent of the parties involved, maintaining the integrity of the contractual agreement.

Other aspects of contract law, such as the requirement for written communication or the need for an acceptance to occur within a reasonable timeframe, while often important in practical scenarios, do not pertain directly to the mirror image rule. Thus, these elements alone are not sufficient for establishing a valid agreement despite their relevance to the overall acceptance process.