World organizations such as the United Nations began to discuss sustainable development in

the

1890s

1970s

1990s

1920s

The correct option is C. World organizations such as the United Nations began to discuss sustainable development in 1990's.

Explanation:

In 1992, the United Nations Conference on Environment and Development held a summit with the main idea of sustainable development. This summit marked the importance of sustainable development to make rapid progress. The main concern of this summit was to check the actions of the humans and their effect on Earth. The summit was of the view that if activities of the humans remain unchecked and unsustainable, then it would be very difficult to live on Earth and the planet might be destroyed.