Janice has set up a sponsored ad for her new line of picture frames. She has selected the keyword “computer” for this ad. Which principle explains why her ad may not display?

Janice's ad may not display due to a lack of relevancy. Amazon's ad system prioritizes showing ads that are highly relevant to a customer's search query. The keyword "computer" is not relevant to "picture frames," so the ad is unlikely to be shown to searchers using that term. This ensures a better shopping experience for customers and more effective ad spend for advertisers. Engagement refers to how users interact with an ad after it's displayed, not whether it displays. Ad spend is the budget allocated, but even with a high budget, an irrelevant ad won't show. Cost-per-click is the price paid for a click, which is determined after an ad is deemed relevant enough to be displayed.