What is the primary distinction between a true Demand-Side Platform (DSP) and an ad network?

The primary distinction between a true Demand-Side Platform (DSP) and an ad network lies in their operational focus and how they facilitate the buying and selling of ad inventory. A DSP is specifically built to serve advertisers on the demand side, allowing them to buy ad inventory in real-time through programmatic bidding. It provides sophisticated targeting, analytics, and optimization capabilities that enable advertisers to effectively reach their intended audiences.

In contrast, an ad network aggregates inventory from various publishers and offers it to advertisers. It operates on both sides, facilitating interactions between demand (advertisers) and supply (publishers). Therefore, the option emphasizing that an ad network focuses on both demand and supply sides accurately reflects its dual role, distinguishing it from a DSP which is tailored specifically for demand-side advertisers.

The other provided choices do not encapsulate this fundamental difference accurately, making the selection of the option about the ad network's dual focus the most representative of the fundamental distinctions between a DSP and an ad network.