Answer:
Through trade.
Step-by-step explanation:
The spread of ideas from Tang and Song China to Europe occurred through trade.
During the Song dynasty, trade between China and Europe was common through Persian and Arab merchants who ended up taking a little of the culture and products produced during that period.
The Tang dynasty, on the other hand, facilitated the entry of European merchants into Chinese territory, which made the trade between these two regions intense and promoted the exchange of ideas and concepts between both.