横向
1
Government elected by the people
4
Succession of rulers from same family
5
Medieval land-for-service system
6
Freedom from outside control
7
Fortified medieval residence
纵向
2
Military blockade of a fortified place
3
Practice of farming and growing food
8
Ancient empire that conquered much of Europe
9
Metal that replaced bronze in tools
10
Ancient Mesoamerican civilization
11
Armed conflict between nations
12
Advanced stage of human society