The correct answer is: 2. horses.
The Han Dynasty's interest in trade with the West began with horses, not silk. The Chinese valued the superior breed of horses from the Ferghana Valley, which was located in present-day Uzbekistan, and they sought to acquire them for military use. The Persian Royal Road, which connected the Persian Empire to the Mediterranean world, became one of the main routes for the trade of horses and other goods. Eventually, the Silk Road emerged as a major trade route, connecting China to the Mediterranean world, and silk became one of the most important commodities traded along the route.