Answer:
d. Colonies were founded with specific trade agreements in place.
Explanation:
The best explanation as to why trade among the colonies flourished is that "Colonies were founded with specific trade agreements in place."
This is evident in the fact that the colonies in the southern part of the thirteen colonies (later the United States) focused on agriculture, while those in the northern part focused on lumbering, shipping, and port.
This thereby led to efficiency in production and services.
