The correct answer is B. By transporting finished goods and raw materials.
Railroads were used in european which had no engines and were used by men where animals pushed wagons which were loaded together with wooden tracks.
When railroad advanced, it helped more in efficiency and safety of coal mines. Railroad made easy the inexpensive way of transportation.
Raw materials, manufactured goods, and food were transported quickly. There was a decrease in cost of production due to railroad and now that the food was in plenty there was increase in population.