Nomadic peoples of the steppes including the Uighurs, the Jurchens (Manchu), the Kazakhs, the Mongols, and the Xiongnu in the north and west of China borders on desert and range-lands. They were the nomadic invaders who controlled and contributed to the collapse of the Han Chinese between 206 BCE and 221 CE in China. The nomadic people controlled the extremely valuable Silk Road trade routes making them unfit to travel which were vital to the success of Chinese governments resulting in an adverse effect to the economy. During the prosperous times, the settled agricultural people of China paid tribute to the troublesome nomads or hired them to provide security from the other tribes while the Emperors offered Chinese princesses as brides to the "Barbarian" rulers to preserve peace.
I know that this isn't what you're looking for, but the answer is not B. The rebellion brought about a decline in race-based slavery. I know because I took the quiz.
