The correct answer is: B. 25 October 1945
The United Nations Organization was established on 25 October 1945 after the Second World War by 51 countries committed to maintaining international peace and security, developing friendly relations among nations and promoting social progress, better living standards and human rights. Due to its unique international character, and the powers vested in its founding Charter, the Organization can take action on the issues confronting humanity in the 21st century, such as peace and security, climate change, sustainable development, human rights, disarmament, terrorism, humanitarian and health emergencies, gender equality, governance, food production, and more.
Option A is incorrect because the United Nations Organization was not established on 24 October 1945.
Option C is incorrect because the United Nations Organization was not established on 26 October 1945.
Option D is incorrect because the United Nations Organization was not established on 25 October 1958.