The United Nations was formed as a result of the actions taken in **World War II**.
**Explanation:**
1. The United Nations (UN) was established on October 24, 1945, after the end of World War II.
2. The aim of creating the UN was to maintain international peace and security, promote cooperation among nations, and prevent future conflicts like the devastating World War II.
3. The founding of the UN replaced the ineffective League of Nations, which was unable to prevent the outbreak of World War II.
4. Through its various agencies and bodies, the UN works towards humanitarian aid, human rights, economic development, and other global issues to foster cooperation and peace among nations worldwide.
Therefore, the United Nations was formed as a direct response to the events and aftermath of World War II, making option D - World War II, the correct answer.
