Explanation:

Credit enhancements in asset-backed securities (ABS) are mechanisms designed to reduce credit risk and improve the credit rating of the securities. Let's analyze each option:

A. Credit tranching - This IS a credit enhancement. Credit tranching involves creating different classes (tranches) of securities with varying levels of seniority and credit risk. Senior tranches have priority in receiving payments and are protected by junior tranches, which absorb losses first.

B. Overcollateralization - This IS a credit enhancement. Overcollateralization occurs when the value of the underlying assets exceeds the value of the securities issued. This provides a cushion against potential losses in the asset pool.

C. Representations and warranties - This is NOT a credit enhancement. Representations and warranties are legal assurances made by the originator or seller of the assets about the quality and characteristics of the underlying assets. While they provide legal recourse if the assets don't meet stated standards, they are not considered structural credit enhancements like tranching or overcollateralization.

Key Points:

• Credit enhancements in ABS include: credit tranching, overcollateralization, cash reserve accounts, excess spread, and third-party guarantees.
• Representations and warranties are contractual obligations rather than structural credit enhancements.
• The question asks for what is NOT a credit enhancement, making C the correct answer.