Which of the following is a characteristic of a unilateral contract?

A unilateral contract is defined by the fact that only one party is obligated to fulfill the terms of the agreement. This is typically seen in scenarios where one party promises to pay for a specific act performed by another party. For instance, if someone offers a reward for the return of a lost pet, the person offering the reward is the only one with an obligation—if the pet is returned, they must pay the reward. The other party is not obligated to perform the act, but if they do, the unilateral contract is fulfilled, and the offeror must honor their promise.

The other options reflect characteristics of different types of contracts or requirements that do not specifically apply to unilateral contracts. For instance, in a bilateral contract, both parties make mutual promises, which creates obligations on both sides. Additionally, while some contracts may need to be in writing, a unilateral contract does not inherently require this form unless specified by law; many can be verbal provided they meet certain elements of contract formation. Lastly, while some terms may be implied by conduct in any type of agreement, this is not a defining characteristic of unilateral contracts alone.