1, because in the pre-Qin period, Shang Yang's political reform transformed slavery into feudal private land system.

2. The Qin Dynasty was centralized, and the feudal system was replaced by the county system.

3. Because Shang Yang's political reform laid the foundation for the feudalization of Qin, which was only a vassal state at that time and the real dynasty was the Eastern Zhou Dynasty, Qin was the first feudal dynasty, but its feudalization began in the pre-Qin period.