Concept:The approval of the annual budget of the United Nations is a financial function given to the main representative body of the organisation.
Explanation:The General Assembly is made up of representatives from all member nations of the United Nations.
It meets once a year, usually from September to December.
Among its duties, the General Assembly discusses and approves the annual budget prepared by the Secretariat.
It also passes resolutions on world peace and security and forwards recommendations to the Security Council.
It approves the appointment of the Secretary-General and admits new members into the organisation.
Therefore, the organ responsible for approving the UN annual budget is the General Assembly, not the Secretariat, Security Council, or Economic and Social Council.
Answer:C. General Assembly