A business wants to forecast reach. Which tool should an advertiser use to perform this task?

When a business wants to forecast reach, the "Estimated daily results" tool is the most appropriate choice. This tool allows advertisers to predict the potential performance of their campaigns by estimating metrics such as the number of impressions and reach based on their targeted audience and budget. It provides insights into how many users may be reached daily, thereby helping businesses plan their advertising strategies effectively.

Analytics, while valuable for tracking and measuring past performance and user behavior, does not provide forecasting capabilities specifically for reach. Attribution focuses on understanding which channels and interactions contribute to conversions, rather than estimating reach. Audience Insights offers information about the characteristics of an audience but does not directly estimate daily reach. Thus, for forecasting needs, "Estimated daily results" stands out as the ideal tool for advertisers.