The correct options are
A Fear of death and destruction of lives and livelihoods due to two World Wars.
B Failure of the League of Nations
D Destruction through arms and nuclear technology.
There were numerous reasons for the establishment of the United Nations. The fear of death and destruction of lives and livelihoods because of the two World Wars, use of deadly weapons, failure of the League of Nations, and need for a permanent peacemaking body were the fundamental reasons. The Cold War started after the establishment of the United Nations.