Race is the answer to your question
Answer:
The real and main reason was The Assassination of Archduke Francisco Ferdinand heir to the throne of Austria-Hungary in his visit in Bosnia. The Hero Gavrilo Princep killed him because he want his country to have independence.
There are also reasons like Imperialism, Nationalism, Militarism and many otherd
Merchants believed that the slaves were less than animals, therefore they needed less than animal conditions.
the answer is colombia cause I did the test! hope this helps!:) :) :)