Answer:
It is called the Columbian Exchange because of Christopher Columbus' widespread transfer of culture, plants, animals, human populations, technology, diseases, and ideas between the Americas, West Africa, and the Old World. This happened between the 15th and 16th centuries
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The Land Ordinance of 1785 made land cheap and affordable. The Land Ordinance established an orderly plan for dividing up the land. The government would first survey the land and divide it into townships. ... Further, each township would be divided into 36 sections of 1 square mile, or about 640 acres, each.
The correct answer is Barack Obama
Before Obama, Bush implemented the policies of prevention and preemption which included fighting preemptive wars against countries that supported terrorism before they had the chance of enabling it. Obama turned away from that and wanted to negotiate more and be diplomatic, instead of just waging new wars.