Answer:
The answer is D, the Columbian Exchange. I hope this helps!
Because the earth's climate is CONSTANTLY in flux and what today is a desert was once a tropical forest.
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They all treated them poorly because they wanted their land.
I would say that these terms illustrate that directions and words like "middle" are relative. For the Europeans China was far east from their point of view, but for China it was in the middle of what was relevant for them. It also shows that each place considers its own place as the center of their world: every other place will be seen through its relation with it.
