Which of the following is not a basic element of a contract?

In the context of contract law, a basic element of a contract includes mutual consent, consideration, and the capacity to contract. Mutual consent refers to the agreement between parties, typically demonstrated through an offer and acceptance. Consideration is the value exchanged between parties, which could be in the form of money, services, or goods. Capacity to contract means that both parties involved have the legal ability to enter into a contract, which generally includes being of legal age and sound mind.

Monetary duty, while it may be a part of some contracts, is not a fundamental element required for the formation of all contracts. Not every contract requires monetary exchange; for example, contracts can involve services or goods without a direct monetary obligation. Therefore, the presence of a "monetary duty" does not satisfy the essential components that universally define a contract, making it the correct answer in this context.