Which of the following is NOT an essential element of a valid contract?

A valid contract requires certain essential elements to be enforceable, and unilateral acceptance is not one of them. A valid contract needs competent parties, which means that those involved must have the legal capacity to enter into a contract. It also requires a legal objective, ensuring that the contract's purpose is lawful and not contrary to public policy. Consideration is another critical element; it refers to something of value that is exchanged between the parties, which can be money, services, or other benefits.

Unilateral acceptance, on the other hand, does not meet the requirements of a valid contract, as contracts typically involve mutual consent, where both parties agree to the terms. This mutual agreement is essential for binding obligations and assures that all parties are aware of and agree to the contract terms. Therefore, the absence of unilateral acceptance as a necessary component helps clarify why it is not considered an essential element of a valid contract.