The correct answer is D. 1974.
The United Nations adopted the Charter of Economic Rights and Duties of States on 12 December 1974. The Charter was adopted by the General Assembly in Resolution 3281 (XXIX), which was adopted by a vote of 120 to 0, with 10 abstentions. The Charter was a response to the perceived inequities of the international economic system, which was seen as benefiting developed countries at the expense of developing countries. The Charter affirmed the sovereign equality of all states and their right to economic self-determination. It also affirmed the right of all states to participate in the international economic system on an equal footing and to benefit from the fruits of international cooperation. The Charter was a significant step forward in the development of international economic law, and it remains an important instrument for developing countries.
Option A is incorrect because the United Nations did not adopt a charter of Economic Rights in 1956.
Option B is incorrect because the United Nations did not adopt a charter of Economic Rights in 1964.
Option C is incorrect because the United Nations did not adopt a charter of Economic Rights in 1969.