Answer:
1. The unification of the six countries complied with the historical trend of development and the people’s demands; 2. The Qin Dynasty increased its national strength through Shang Yang’s reform and laid the foundation for the unification of the six countries; 3. Qin Shi Huang employed talents and promoted the unification; 4, donghangu, Xisanguan, Beixiaoguan, Nanwuguan. The river is its protectorate, and Xiao Mountains is its barrier mountain. The plains of the six countries are joined and the war is on.
Step-by-step explanation: