Final answer:
The sentence "Dragon boat racing is more than 2,500 years old" best shows the significance of the sport in Chinese culture, as it highlights the long-standing tradition and cultural heritage of dragon boat racing.
Step-by-step explanation:
The sentence that best demonstrates dragon boat racing's significance in Chinese culture is "Dragon boat racing is more than 2,500 years old." This sentence directly highlights the historical roots and enduring importance of dragon boat racing within Chinese traditions. It suggests that the practice has been an integral part of the culture for millennia, thereby establishing its significance. Additionally, dragon boat racing is associated with the Dragon Boat Festival, a traditional holiday in China that is closely tied to historical figures, rituals, and foods such as zongzi, further underscoring the cultural importance of the event.