In what situation might a unilateral contract be enforced?

A unilateral contract is a type of agreement in which only one party makes a promise or commitment, and that promise is contingent upon the performance of a specific act by the other party. The nature of a unilateral contract is such that it becomes enforceable when the act is performed.

In this context, the correct answer highlights that enforcement occurs when one party performs an act in exchange for the promise made by the other party. For instance, if someone offers a reward for the return of a lost pet, the offeror is promising a payment if the act of returning the pet is completed. The contract is not binding until the act of returning the pet is executed, illustrating the one-sided nature of the promise.

Other answer choices focus on conditions that either require mutual agreements or specific preconditions which do not apply to the concept of unilateral contracts. For instance, a mutual agreement where both parties have fulfilled their promises relates more to bilateral contracts, where each party's performance is essential. Similarly, drafts by both parties and conditions precedent imply a level of mutuality and obligations that are not characteristic of unilateral contracts. Thus, the core feature of how a unilateral contract works and what makes it enforceable directly aligns with the act performed in response to the promise made.