The question asks about the location where the world's first environmental conference was held. Let's look at each of the options and determine which is correct:
- Brazil: While Brazil is known for being the host of the Earth Summit (also known as the Rio Summit) in 1992, it was not the location of the first environmental conference.
- Stockholm: The United Nations Conference on the Human Environment, commonly referred to as the Stockholm Conference, was held in Stockholm, Sweden, from June 5-16, 1972. It was indeed the first major international conference on environmental issues.
- New York: New York is the headquarters of the United Nations, but it was not the location of this first environmental conference.
- London: London has not hosted a foundational environmental conference comparable to the Stockholm Conference.
Given the above analysis, the correct answer to the question is indeed Stockholm. This conference marked a significant cornerstone in international environmental diplomacy, laying the foundation for subsequent environmental dialogues and policy developments globally.