I believe that the three levels are:
1) primary or extractive: getting the resources. this includes for example producing milk (milking cows)
2) secondary: manufacturing: packaging the milk and treating it
3) tertiary: providing a service, for example bringing the milk to people's home!
Stop burning fossil fuels
Stop Deforestation
Small steps which we can do would be:
1.Plant at least one plant or tree.
2.Start using eco-friendly products
3.Stop wasting electricity and water for unnecessary reasons
THIS COULD HELP TO SAVE OUR ENVIRONMENT
Answer:
It's the water cycle as simple as that
The Crusades lasted from 1095 - 1291.