Answer :
The question is asking to state the reason why the chinese trade silk for horses from ferghana, and base on my further research and investigation, the reason would be that The horses of Ferghana were
superior to the horses bred in China.
Wu-Ti called the horses “heavenly”
and even wrote a poem about them.
The main transport at that time was Ferghana's horses and horses had a very high quality and Wi-ti loved them and wanted very much them, but to obtain horses of such high quality, it was necessary to exchange for a product of similar value , in this case, the Chinese silk.
In the distant past, the Chinese have learned how to make silk from the white fiber of the cocoons of silkworms. Only the Chinese knew how to manufacture it, and they kept this closely guarded secret. When they made contact with the cities of the West, they found people willing to pay dearly for the silk.
