D- all of the choices are correct
The correct answer to this open question is the following.
You did not provide any excerpt, text, reference, or context to answer this question. That makes it difficult to exactly what you are referring to.
However, trying to help you and doing some research we can say the following.
One historical event or development in the period 1830 to 1860 that is not explicitly mentioned that could be used to support Hahn’s interpretation is how the United States became the engine of the ecom¿nomy of the planet because of its industrial capacity. How the Gross Domestic Product grew and the many opportunities the US offered to immigrants to work in major industries such as the Standard Oil Company of John F. Rockefeller, or the Steel company of Andrew Carnegie.
Innovations and the use of technology helped industries to earn more profits and invest that money in the creation of jobs and the spread of their operations nationwide.
