Explanation:

Seals (Option B) excavated from the Indus Valley Civilization are considered strong indicators of commercial and economic development. These seals, often made of steatite and inscribed with pictographic scripts and animal motifs, were likely used for marking ownership of goods, facilitating trade, and administrative purposes, suggesting an organized economic system. While Pottery (Option A), Boats (Option C), and Houses (Option D) are also important archaeological finds, seals provide more direct evidence of trade and economic transactions.