Which of the following statements about private marketplaces (PMPs) are true?

Private Marketplaces (PMPs) are indeed invitation-only, meaning specific publishers offer inventory to selected buyers, providing more control and transparency than open exchanges. They allow advertisers broader access to premium third-party supply that might not be available on the open market, often at negotiated rates. PMPs extend the benefits of programmatic advertising—like real-time bidding, targeting, and optimization—to these specific, curated publisher deals, combining automation with direct relationships. The statement about Amazon's header-bidding integrations is incorrect because while header bidding is a common programmatic technique, it's not exclusive to or a defining characteristic of PMPs themselves, nor is it solely an Amazon-specific feature for PMPs.