Chief Administrative Officer of the U.N.
The Chief Administrative Officer of the United Nations is referred to as the Secretary General. The Secretary General is the highest-ranking official in the United Nations and is responsible for the overall administration of the organization.
Answer: B
Explanation:
The role of the Secretary General can be further explained with the following details:
- The Secretary General is appointed by the General Assembly upon the recommendation of the Security Council.
- The Secretary General acts as the chief administrative officer of the United Nations and is responsible for the management of its operations and resources.
- The Secretary General represents the United Nations in various international forums and interacts with member states, non-governmental organizations, and other stakeholders.
- The Secretary General also plays a crucial role in diplomatic negotiations, conflict resolution, and promoting international cooperation.
- The current Secretary General of the United Nations is António Guterres, who assumed office on January 1, 2017.
In conclusion, the Chief Administrative Officer of the United Nations is the Secretary General.

Secretary General of the U.N.
The Chief Administrative Officer of the United Nations is the Secretary General. The Secretary General is the head of the UN Secretariat, which is the administrative arm of the organization responsible for implementing the decisions of the UN's main bodies such as the General Assembly and Security Council.

Role of the Secretary General
The Secretary General plays a crucial role in representing the United Nations and its values to the world. They are responsible for overseeing the day-to-day operations of the organization, managing its staff, and coordinating the work of its various agencies and programs.

Appointment Process
The Secretary General is appointed by the General Assembly upon the recommendation of the Security Council. The appointment is made for a renewable term of five years. The selection process is guided by the principle of geographical rotation, with candidates from different regions of the world being considered for the position.

Current Secretary General
As of 2021, the Secretary General of the United Nations is António Guterres. He assumed office on January 1, 2017, succeeding Ban Ki-moon.

Importance of the Position
The Secretary General is a key figure in global diplomacy, often acting as a mediator in international conflicts and representing the UN in high-level meetings with world leaders. The role requires strong leadership, diplomatic skills, and a deep commitment to the principles of the United Nations.