Which of the following technological developments was most responsible for a massive increase in productivity during the Gilded Age?
Invention of the light bulb
Invention of the telephone
Expansion of the railroad system
Mass production of steel

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