What role did andrew carnegie play in bog business

He left the railroad in 1865 to focus on his other business interests, including the Keystone Bridge Company. By the next decade, most of Carnegie's time was dedicated to the steel industry. His business, which became known as the Carnegie Steel Company, revolutionized steel production in the United States.

just like you man, i personally think its either c or d

explanation:

but good luck with the test man

america