Answer:
The correct answer is letter "D": began creating or consolidating their fortunes during the Civil War.
Step-by-step explanation:
American Civil War (1861-1865) was one of the bloodiest conflicts over slavery held between the northern and the southern states. Eventually, the Confederate States -pro-slavery states, surrendered at the cost of more than 620 000 deaths over the 4 years the war lasted.
During the war years personalities such as Andrew Carnegie (1835-1919) and John D. Rockefeller (1839-1937) consolidated their fortunes since the first, and iron businessman and the second, oil investor, saw a rise in the demand of their goods because of their need in the battlefield -armors for gunboats, cannons and frames.