Which of the following is the most accurate analogy for a display advertising network?

A display advertising network acts as a marketplace because it connects advertisers who want to show ads with publishers who have ad space available on their websites or apps. It automates the buying and selling of ad impressions, making it efficient for both parties. "A targeting option for publishers" is incorrect because while ad networks offer targeting, their primary function is broader than just targeting; they facilitate the entire transaction. "A payments system for online ad campaigns" is also incorrect; while ad networks handle payments, this is a secondary function to their core role of connecting buyers and sellers of ad space.