Which contract involves a promise by one party contingent on the other party performing a specified act?

• A. Bilateral Contract
• B. Unilateral Contract
• C. Executory Contract
• D. Implied Contract

Answer: (B)

Unilateral contracts are built on a promise that is triggered by performance. In this setup, one party promises to pay or compensate only if the other party carries out a defined act, and the contract is created and becomes enforceable when that act is actually performed. A classic example is a reward offer: “I will pay $100 to whoever finds my lost dog.” The offeror has promised payment, but acceptance occurs only through the completion of the act by the offeree.

In contrast, a bilateral contract rests on promises exchanged by both sides, an executory contract describes a contract still in the stage where duties remain to be performed (regardless of the promise structure), and an implied contract arises from the parties’ conduct rather than an explicit promise contingent on performing an act.