Explanation:

- Condition: A condition is an essential term of a contract. If breached, it allows the affected party to terminate the contract and seek damages. It's central to the agreement's main purpose.

- Warranty: A warranty is a stipulation collateral to the main purpose of a contract. It is a secondary obligation. Breach of a warranty entitles the affected party to claim damages but not to terminate the contract.

- Obligation: An obligation refers to a duty or commitment under a contract. It can be either a condition or a warranty.

- None of the above: This option suggests that none of the provided choices correctly answers the question.

Warranty is correct. A warranty is indeed collateral to the main purpose.