What is the maximum number of headlines an advertiser can provide for their Responsive Search Ads?

The selected answer option is correct because 15 headlines is the maximum number of headlines an advertiser can provide for their Responsive Search Ads (RSAs) in Microsoft Advertising. RSAs allow advertisers to input multiple headline variations (up to 15) and descriptions, which the platform's machine learning system will automatically test and combine to create the most effective ad combinations based on user searches. By providing up to 15 headlines, advertisers can maximize their ad’s reach and relevance, as the system will dynamically choose the best-performing combinations to optimize the ad for each individual search query. This flexibility helps improve ad performance, making it more likely to match the search intent of potential customers. Other options, like 4 or 10 headlines, are incorrect because they fall short of the maximum limit set by Microsoft Advertising for RSAs.