Which of the following solutions is a free way for brands to feature their product portfolio and tell their brand story to educate and build long-term relationships with shoppers.

The correct answer is Brand Stores because this solution provides brands with a dedicated space on Amazon to showcase their product portfolio and share their brand story without any associated costs. By utilizing Brand Stores, companies can create an immersive shopping experience that educates customers about their offerings and helps build long-term relationships. In contrast, Sponsored Brands are paid advertising solutions that promote products through ads, while the Amazon Shopping Panel is primarily focused on customer engagement and feedback rather than providing a platform for showcasing a brand's entire product range, making Brand Stores the most suitable option for featuring products and fostering customer relationships for free.