What does this map illustrate, and what effect did it have on the region?

A: the Silk Road; it contributed to economic growth and exchange of ideas because it linked developing civilizations with each other

B: the Great Wall to the north and a network of coastal defense ports to the south; they helped maintain China's isolation because they protected China from invasion and trade

C: the Silk Road; it provided economic opportunity for traders because it allowed valuable goods such as silk and spice to travel to China

D: the Great Wall to the north and a network of coastal defense ports to the south; they helped the Chinese army move quickly throughout the empire