Detailed Solution:
The correct answer is “Paris”.
The United Nations Conference on Climate Change, COP21, was held in Paris, France in 2015.
It was also known as the 2015 Paris Climate Conference and was a landmark event in the international efforts to combat climate change. The conference brought together representatives from 196 countries to negotiate and adopt a legally binding agreement on climate change.
The Paris Agreement, which was the result of the conference, sets a goal of limiting global warming to well below 2 degrees Celsius above pre-industrial levels, and pursuing efforts to limit the temperature increase to 1.5 degrees Celsius.