The Earth Summit was held at Rio-de Janeiro, Brazil in which year?

June 1992

The correct answer is option (4) - June 1992

The growing focus on environmental issues within the arena of global politics was firmly consolidated at the United Nations Conference on Environment and Development held in Rio de Janeiro, Brazil, in June 1992. This was also called the Earth Summit.
The summit was attended by 170 states, thousands of NGOs and many multinational corporations. The Rio Summit produced conventions dealing with climate change, biodiversity, and forestry, and recommended a list of development practices called ‘Agenda 21’