The first Secretary-General of the United Nations was Trygve Lie. He was a Norwegian politician who served from 1946 to 1953. Lie was a strong advocate for the United Nations and its mission to maintain international peace and security. He also played a key role in the establishment of the United Nations Educational, Scientific and Cultural Organization (UNESCO).
Dag Hammarskjöld was the second Secretary-General of the United Nations. He served from 1953 to 1961. Hammarskjöld was a Swedish economist and diplomat who was known for his work on international development and economic cooperation. He was also a strong advocate for human rights and the rule of law.
U Thant was the third Secretary-General of the United Nations. He served from 1961 to 1971. Thant was a Burmese diplomat who was known for his work on decolonization and the peaceful resolution of conflict. He was also a strong advocate for the rights of developing countries.
Kurt Waldheim was the fourth Secretary-General of the United Nations. He served from 1972 to 1981. Waldheim was an Austrian diplomat who was known for his work on human rights and the rule of law. He was also a strong advocate for the peaceful resolution of conflict.
The correct answer to the question is C. Trygve Lie.