The correct option is 1 only. Agenda 21 is indeed a global action plan for sustainable development, adopted at the United Nations Conference on Environment and Development (UNCED) held in Rio de Janeiro in 1992, not during the World Summit on Sustainable Development in Johannesburg in 2002. The initiative outlines strategies for sustainable development across various sectors and emphasizes local implementation, involving all levels of government and sectors of society. Understanding this framework is crucial for UPSC candidates as it highlights international efforts toward sustainability and governance, key themes in global environmental policy.