The answer is B. I am 100% sure and know this from experience.
The correct answer is C. Manufacturing.
Explanation
The new technologies developed in the North were on a par with the thousands of inventions that occurred during the Industrial Revolution. For this reason, the economic activity that benefited the most from technological advances was manufacturing, which became massive thanks to them. These new technological inventions allowed the growth of different manufacturing companies that welcomed the economy and efficiency offered by new machines and technology at that time. Therefore, the correct answer is C. Manufacturing.
the natural barriers were the himalaya mountains
