Summarize the status of Qin Shihuang, Emperor Taizong and Emperor Kangxi in the history of China in one sentence, and briefly describe your reasons.
Qin Shihuang initiated the peak of Guan Zhen. Emperor Kangxi was the first emperor in China to unify the feudal country. China's feudal system became more powerful. Emperor Taizong was a promising emperor in China (the early Tang Dynasty was the most prosperous period in China) (but Xuanzong began to decline again). Emperor Kangxi's reign was the longest, and it was the last powerful time of China's feudal system.