The correct answer is C. The Secretariat.
The Secretariat is the chief administrative office of the United Nations. It is headed by the Secretary-General, who is appointed by the General Assembly on the recommendation of the Security Council. The Secretariat is responsible for carrying out the day-to-day work of the United Nations, including preparing reports, organizing conferences, and providing technical assistance to member states.
The International Court of Justice is the principal judicial organ of the United Nations. It is composed of 15 judges, who are elected by the General Assembly and the Security Council. The Court has jurisdiction to settle legal disputes between states, and to give advisory opinions on legal questions referred to it by authorized UN organs and specialized agencies.
The General Assembly is the main deliberative organ of the United Nations. It is composed of all member states, and each state has one vote. The General Assembly meets in regular sessions every year, and in special sessions when necessary. The Assembly’s functions include discussing and making recommendations on international issues, and approving the UN budget.
The Trusteeship Council is a UN body that was established to oversee the administration of trust territories, which were territories that were not self-governing and were placed under the administration of a trusteeship agreement. The Trusteeship Council has now completed its work, and all trust territories have achieved self-government or independence.