Final answer:
A significant result of the Columbian Exchange was the Spread of diseases between the Old and New Worlds, which led to massive depopulation of indigenous peoples.
Step-by-step explanation:
A significant result of European exploration and the subsequent Columbian Exchange was the spread of diseases between the Old World and the New World, as stated in option A. This exchange had a profound impact on global populations, especially through the introduction of European diseases like smallpox and influenza to the indigenous peoples of the Americas, who had no immunity to these illnesses. This led to massive depopulation in the New World.
In addition to diseases, the Columbian Exchange facilitated the transfer of crops, animals, and cultural traditions across continents, reshaping economies and societies in both hemispheres. The arrival of foods such as potatoes and tomatoes in Europe and the introduction of horses and cattle to the Americas were among the key exchanges that occurred. The widespread exchange and adaptation of agricultural products increased the variety of available foods, which subsequently boosted agricultural productivity.