If Vlad the appraiser runs into a valuation issue that he's not sure how to address, which group will be most likely to provide guidance for him?

The Appraisal Practices Board (APB) is the most appropriate group for Vlad to turn to when he encounters a valuation issue. This board is specifically established to identify and respond to valuation issues and provide guidance in addressing various appraisal challenges. They offer advisory opinions and resource materials that are directly applicable to appraisal practice and promote understanding of valuation issues within the industry.

While the other groups listed may have valuable resources or positions regarding broader appraisal standards, the APB's primary focus is to provide support and best practices concerning specific appraisal problems. This specialized role makes the APB the ideal choice for appraisers seeking help with complex valuation issues.