Which of the following is a declaration from an independent third party that lends credibility to the part of the organization undergoing the review and is required as part of an audit?

An executive summary is a high-level overview of a report, usually written by the report's authors, not an independent declaration of credibility.

Client acceptance is the client's agreement to the terms or findings of a project, not an independent third-party declaration.

Attestation of findings is a professional service where an independent third party provides a written report confirming the accuracy and reliability of assertions made by management regarding compliance, controls, or other subject matter. In an audit, this external validation lends credibility to the findings and the organization's adherence to standards or regulations.

Lessons learned are insights gained from a project, usually documented internally for future reference, and do not involve an independent third-party declaration for credibility in an audit.