What are the three main causes of world war 2?

The 3 significant causes to World War 1 would be:1. Treaty of Versailies, which forces Germans into accepting Full Blame for WWI. 2.This caused Germany to lose a lot of its lands. 3. Forced them to pay restitution for war dameges to countries like France, and Great Britain ect. 4. (just for the info) This made their leader very angry and it started a whole new perspective upon the nations view point. 

Um well north korea is a very harsh place because students go to school for 24 hours and almost never rest and the president is well i think sends to much bomb that’s what i think

They were busting people when they really didn't need to