Through which platform can a brand or agency manage its programmatic campaigns?

A Demand-Side Platform (DSP) is the correct answer because it is the software platform used by advertisers (brands and agencies) to manage and automate the buying of ad impressions across multiple ad exchanges, supply-side platforms, and publishers. DSPs allow advertisers to set targeting parameters, bids, and budgets for their programmatic campaigns. An SSP/Exchange (Supply-Side Platform/Exchange) is used by publishers to sell their ad inventory, not by advertisers to buy it. A DMP (Data Management Platform) is used to collect, organize, and activate audience data, but it doesn't directly manage the buying of ad impressions; it feeds data into a DSP to enhance targeting.