Final answer:
The ad setting to ensure a qualified user will always receive a city-targeted ad over a country-targeted ad for the same placement is Priority. It ranks ads to show the most relevant based on location and is crucial for precise ad targeting and performance.
Step-by-step explanation:
The ad setting that ensures a qualified user will always be served a city-targeted ad first over a country targeted ad when both ads are assigned to the same placement is Priority. This setting allows advertisers to rank ads in order of importance, ensuring that the most relevant ads are shown to users based on their location. City-targeted ads tend to have higher priority over country-targeted ads on platforms that support such detailed targeting options.
In the context of online advertising, Priority is useful for campaigns where multiple ads compete for the same ad space. By setting a higher priority on the city-targeted ad, it will take precedence over the country-targeted ad, leading to more precise targeting and potentially better performance for the advertiser.