Answer
All of the above refers to the Xiongnu, Yuezhi, and Qiang. Towards the end of Emperor Wen's reign, the Xiongnu were subdued by the Han dynasty after a series of military campaigns. The Yuezhi were a nomadic people who had previously been defeated by the Xiongnu, but they were able to re-establish themselves in the Tarim Basin after the Xiongnu were defeated.