Detailed Solution:
The correct answer is “Sustainable development”.
Agenda 21 is a comprehensive action plan developed at the 1992 Earth Summit (Rio Summit) focused on promoting sustainable development globally. It outlines strategies for achieving sustainable development through environmental protection, social equity, and economic growth.
The United Nations Conference on Environment and Development, also known as the Rio de Janeiro Conference or the Earth Summit, was a major United Nations conference held in Rio de Janeiro from 3 to 14 June 1992.