B. The Grand Canal was constructed to unite northern and southern China
D. The Sui dynasty reunited China in the sixth and seventh centuries by combining existing laws into a single legal code.
Explanation:
The Sui dynasty followed the Southern and Northern Dynasties and preceded the Tang dynasty in China. It ended with about four centuries of rule of the shared mandate between self-proclaimed dynasties in both the north and the south.
The Suí dynasty is often compared to the previous Qin dynasty in terms of their possessions and the cruelty of their achievements. The early collapse of the Sui dynasty has been attributed to the tyrannical demands of the government on the people, who endured the terrible burden of taxes and compulsory labor. These resources were exhausted with the construction of the Grand Canal -a monumental engineering challenge- and in the undertaking of other construction projects, including the reconstruction of the Great Wall of China. Weakened by costly military failures against Korea in the early seventh century, the dynasty was disintegrated by a combination of popular revolts, disloyalty and assassinations.
