Analysis of test questions: students should grasp the characteristics of this period of history in a macro and comprehensive way. According to what I have learned, during the Three Kingdoms, the Jin Dynasty and the Southern and Northern Dynasties, the regimes were separated, but in order to strengthen their strength, each regime took various measures to develop the economy, and the society was still progressing. Especially in the Southern and Northern Dynasties, Emperor Xiaowen's reform further promoted national integration, and the separation of regimes coexisted with local unity, and the country showed a unified trend. Analyze and compare the four options, so choose item C.