7 April is observed as –

World Cancer Day
United Nations Day for South-South Cooperation
World Telecommunication Day
World Health Day

The correct answer is: World Health Day.

World Health Day is observed on 7 April every year. It is a global health awareness day celebrated under the sponsorship of the World Health Organization (WHO). The day is intended to draw worldwide attention to a major health issue. Each year, a theme is chosen for the day. The theme for 2023 is “Our planet, our health”.

World Cancer Day is observed on 4 February every year. It is a global campaign led by the Union for International Cancer Control (UICC). The day is intended to raise awareness about cancer and to encourage its prevention, early detection, and treatment.

United Nations Day for South-South Cooperation is observed on 12 September every year. It is a day to celebrate the achievements of South-South cooperation and to promote its further development. South-South cooperation is a form of international cooperation between developing countries. It is based on the principles of solidarity, mutual benefit, and respect for national sovereignty.

World Telecommunication Day is observed on 17 May every year. It is a day to celebrate the achievements of the telecommunications industry and to promote its further development. Telecommunications is the transmission of information over long distances. It includes the technologies of telephony, telegraphy, radio, television, and the Internet.