Which of the following is NOT a classification of a contract?

The classification of contracts typically includes various types based on their characteristics. Unilateral contracts involve one party making a promise in exchange for an act, while bilateral contracts involve mutual promises between two parties. Adhesion contracts are typically standardized agreements imposed by one party, leaving little to no room for negotiation.

Enduring, however, is not recognized as a standard classification of contracts. It does not accurately describe any type of contract based on promise exchange, conditions, or legal enforceability. Unlike the other classifications, which are established in contract law, enduring does not convey any specific characteristics that would help in categorizing contracts. Thus, selecting it highlights a clear distinction from recognized contract classifications.