The correct answer is: D. International Human Solidarity Day
International Human Solidarity Day is observed on December 1 each year. It was proclaimed by the United Nations General Assembly in 2005 to promote human solidarity and understanding among peoples and nations. The day is also a reminder of the importance of international cooperation in addressing global challenges such as poverty, hunger, and climate change.
World day for War Orphans is observed on June 6 each year. It was established by the United Nations General Assembly in 2002 to raise awareness of the plight of war orphans and to promote their rights and welfare.
United Nations Day for South-South Cooperation is observed on December 19 each year. It was proclaimed by the United Nations General Assembly in 1986 to promote cooperation among developing countries. The day is also a reminder of the importance of South-South cooperation in achieving the Millennium Development Goals.
World AIDS Day is observed on December 1 each year. It was established by the World Health Organization in 1988 to raise awareness of the HIV/AIDS pandemic and to promote action to combat it.