What were some effects of the columbian exchange?

Due to the Columbian Exchange, Africa's population declined, the Americas flourished with plants from Europe and wealth flowed in the European economy.

Explanation:

The Columbian Exchange was the process that took place between the 15th and 16th centuries in which agricultural products, technological advances and other resources of the New World (the American continent) were made known in the Old World (Europe, Africa and Asia) and vice versa. More extensively, it also includes demographic changes and even diseases.

i think the answer is c, rivers.

explanation:

sometimes, borders fall along natural boundaries like rivers or mountain ranges. for example, the boundary between france and spain follows the crest of the pyrenees mountains. for part of its length, the boundary between the united states and mexico follows a river called the rio grande. the borders of four countries divide africa’s lake chad: niger, chad, cameroon, and nigeria.

the answer is a. laws were enacted in the aftermath of the plot to make it harder to free slaves,increasing sectionalism