The correct answer is - B. Agenda 21.
The Agenda 21 is an initiative pushed by the United Nations in order for the humanity to aim and develop in a sustainable way.
This initiative is a product of the Earth Summit that has taken place in Rio de Janeiro, Brazil, in the year of 1992.
It is a nice initiative, and the humanity should indeed focus on sustainability, as the natural resources that are most widely used are no-renewable, and also they are damaging the environment from which everyone is dependent for survival.
While some countries have put a lot of effort in this, some just ignore it totally in order to boost their economies.