An appraiser's report must always comply with which standard related to their profession?

The correct answer is the Uniform Standards of Professional Appraisal Practice, commonly known as USPAP. USPAP represents the national standards set forth for appraisers in the United States, establishing a framework for professional conduct in the industry. This includes guidelines on ethical behavior and performance standards which must be adhered to in delivering appraisal reports.

Compliance with USPAP ensures that appraisers maintain a level of professionalism and integrity in their work. The standards outline essential components such as competency, ethics, and the scope of work necessary for credible appraisal results. Any appraiser conducting valuations must follow these standards to ensure that their reports are reliable and accepted by clients, regulatory bodies, and other stakeholders involved in real estate transactions.

In contrast, ASCA Standards, AIR Guidelines, and Industry Best Practices are relevant in specific contexts or specialties within the broader field but do not serve as the overarching regulatory framework for all appraisers. Hence, while adherence to these may be beneficial or required in certain situations, it is USPAP that establishes the fundamental standards applicable across the profession in all appraisal contexts.