Detailed Solution:
The correct answer is “It is an action plan for the conservation of global environment in 21st century.”.
Agenda 21 is an action plan for the conservation of global environment in the 21st century.
It is a non-binding action plan adopted by the United Nations at the Earth Summit in Rio de Janeiro in 1992. It outlines a comprehensive set of goals and strategies for sustainable development, addressing issues such as climate change, biodiversity loss, and poverty.