What legal consequence occurs when a specific event on which a contract relies fails to happen?

When a specific event that a contract relies upon fails to occur, the legal consequence generally entails the automatic termination of the contract. This situation is often described as a "condition subsequent," which is a provision in a contract that specifies that if a certain event does not happen, the contract will end.

In many contracts, parties include conditions that must be met for the agreement to remain valid—if these conditions are not satisfied, the obligations outlined in the contract can no longer be enforced. Therefore, when such an event does not happen, it serves as a legal trigger that ends the parties' contractual duties, often without the need for either party to fulfill further obligations.

The other options do not align with this principle. For instance, if the contract were to continue under modified terms, this would imply a mutual agreement to adjust the existing terms, which typically doesn't happen in case of a fundamental failure of a condition. Renegotiation of the contract might occur, but it would not be a direct legal consequence of the event's failure; it would depend on the willingness of the parties involved. Lastly, stating that the contract is entirely unaffected contradicts the concept of conditions within contract law, as a failed condition usually leads to terminating its enforceability.