A study of the policy of "ethnic cleansing" in Bosnia and the Holocaust in Europe would suggest that (1) world opinion is effective in stopping genocide
(2) countries generally use reason and negotiation in dealing with important ethnic issues
(3) anti-Semitism and ethnic hatred remain powerful forces in the modern world
(4) military leaders cannot be held responsible for acts committed during wartime

(3) anti-Semitism and ethnic hatred remain powerful forces in the modern world

(1) world opinion is effective in stopping genocide: the world opinions didn't stop the genocides. They still occurred.

(2)countries generally use reason and negotiation in dealing with important ethnic issues:  Nope. Killing thousands and millions of people is not using reason and negotiation. Its using violence and propaganda. This is definitely incorrect.

(3)anti-Semitism and ethnic hatred remain powerful forces in the modern world: Its true. The Holocaust occurred because of anti-Semitism and it wasn't too long ago*. The "ethnic cleansing" in Bosnia was a result of ethnic hatred. And it too wasn't that long ago*.

(4) military leaders cannot be held responsible for acts committed during wartime: Definitely incorrect. They really can absolutely be held accountable for acts committed during wartime. And they were.

* "wasn't that long ago" explains, and indicates that it occurred in the modern world.

the answer to your question is:

strong-mayor system

hernan cortes;

explanation: