The narrative report is the best answer selection provided, and is the most thorough appraisal report format. It documents all of the reasoning and data involved in the appraisal process in a long-form format. Addenda can also be attached, making the total length of the narrative report near that of a book. A narrative report is most commonly used for commercial properties and residential properties containing greater than four units. A short form report is considerably abridged compared to a lengthy narrative report. A letter report usually contains only the appraiser’s investigations and analyses.