The defensive feature that the passage refers to is the Great Wall of China. The oldest existing section of wall was built by the Qi dynasty, and it was started around 685 BC. Other dynasties continued the construction, such as the Wei, Zhao, Han, Yan and Zhongshan.
One of the factors that contributed to the decline of the Han empire was the fact that several local military rulers began amassing too much power. The empire was fragmented, and divided into three spheres of influence: that of Cao Cao, that of Sun Quan and that of Liu Bei.
1. The construction of the Great Wall began in the Qin dynasty under the first emperor Shi Huangti. The answer is B: Qin.
2. A and B do not explain some of the reasons the empire declined. A and B are eliminated. Tax revenue went down, but it wasn’t exactly due to tax cuts. People just started disobeying the rules. There were emperors that ruled for their own amusement. The scholars and generals were searching for lots of power. The answer is C.
