What were the four main causes of world war i? give me a simple explanation about each cause of world war i.

1. The agreement of Defense Alliance which is contained if one country being attacked then the allies must helping.
2. Imperialism which is mean when a country try to colonize another country to take all the natural resources for themself
3.Militarism which is mean the war of weapon.
4. Nasionalism it caused by Slavia nation in Bosnia and Hergezovina don't want to be a part of Austria-Hungaria, but they want to be a part of Serbia, but mostly every countries in Europe were trying to prove their  domination and their power

(sorry my english not really good,,hope you can understand)

 

In roman times most people lived in small cities, while during the middle ages most people lived in the countryside. all of the following are reasons forthis change except    people fled the urban centers because they had become too crowded and unsanitary, all otehr are correct but we must remebr that it refers to teh early middle ages