Answer:
More of the world's population is now concentrated in heavily populated urban areas known as cities. This is quite a contrast from the past when or native groups were either farmers or — hunters and gatherers who moved between places in search of food.
Advanced technology has led to the integration of world economics and cultures, in the world's more developed countries. This integration requires increased sinergies, the responsible use and management of natural resources.
Explanation:
The ozone layer. The gas it is made of is formed by 3 oxygen atoms.