An aleatory contract is a type of contract where the performance of one party is contingent upon the occurrence of an uncertain event. In this scenario, the uncertain event is the insured's claim for medical expenses, which occurs after only one premium payment has been made. The insurer's obligation to pay the claim is dependent on this uncertain event happening. This contrasts with an adhesion contract, where one party has more power and dictates the terms, and a unilateral contract, where one party makes a promise in exchange for the other party's performance. The term 'mismatched contract' is not commonly recognized in contract law, making it an incorrect choice in this context.