The right answer is b.rapid economic growth and social change.
The Gilded Age (1870-1900) was a period that followed the end of the secession war and the post-reconstruction period. It is marked by a strong economic and populational growth with no precedents. The causes of the rapid industrialization abundance of supply of raw materials, plenty of labor supply, both via migration, and immigration and the advent of new technologies, innovations that raised the productivity. Besides that, we can also point out the work of talented businessmen combined with a friendly government promoting laissez-faire, subsidies and international high tariffs.
