Final answer:
The Silk Road trade routes are most closely associated with the theory of cultural diffusion.
Step-by-step explanation:
The event most closely associated with the theory of cultural diffusion is B) The Silk Road trade routes. The Silk Road was a network of trade routes that connected Europe, Africa, and Asia, allowing for the exchange of goods, ideas, and cultural practices. It played a significant role in spreading cultural influences and innovations across different regions.