Answer:
(C) Persians traded directly with the Chinese along the Silk Road.
Explanation:
The silk road that is developed in China consisted the main and most important trading routes in the world from the second until the 18th century. Many countries benefited from that route to receive all kind of goods and especially silk, and Persia was the country that traded directly with China.
After the development of Silk road, the routes in Iran improved as well and started growing allowing higher connection, and the trade of several items. The most famous ones were jewels, aromas and spices that were mostly used and shipped to Persia back then.