What Song Chinese practices resulted in a more unified Chinese culture?

Tang rulers further strengthened the central government of China. They expanded the network of roads and canals begun by the Sui. This helped to pull the empire together. They also promoted foreign trade and improvements in agriculture.

Explanation:

I know the first one but not the second part sorry.

Here it is:

Many opponents of busing claimed the existence of "white flight" based on the court decisions to integrate schools. Such stresses led white middle-class families in many communities to desert the public schools and create a network of private schools.

Explanation: