All of these are describing
a.) the silk roads
b.) scientific discovery
c.) the columbian exchange
d.) circumnavigation of the world

C.) The Columbian exchange

Explanation:

It is called the Columbian exchange to the process occurred between the fifteenth and sixteenth centuries in which agricultural products and other foods of the New World (the American continent) in the Old World (Europe, Africa and Asia) and vice versa were made known. A broader definition also includes technological advances, demographics and even diseases. The term was coined by the American historian Alfred Crosby in 1972 in his book The Columbian Exchange

wait history, who want to talk about history, boring.