Respuesta :
The correct answer is D. It helped him predict that the demand for steel to build railroad tracks and bridges would grow.
Explanation:
Andrew Carnegie was one of the most prominent businessmen in the steel industry. His beginning in this area is believed to be related to his job in the Pennsylvania Railroad Company when he was only 18 years old. This is because in this company Carnegie noticed the railroad industry was expanding, which allowed him not only to get an important job position at this company but to predict in a near future more steel would be needed and investing in this area would lead to high profit. Indeed, from this point, Carnegie began to invest in steel-related industries including railroad tracks, bridges, etc.