Some scientists believe the greatest scientific discovery of all time is

the nutritional benefits of chocolate
for every action there is an equal and opposite reaction
gravity is the natural consequence of a curve in space-time
the sun revolves around the earth

Who ever answers first gets ! trade in the vedic age led to a. the rise of kingdoms because of the importance of controlling land and long-distance travel routes b. the building of an extensive system of roads because of the difficult terrain c. the creation of a large banking class because of the need to exchange different currencies d. the development of a centralized government that controlled the economic decisions of its people