Carnegie build his monopoly by cutting costs to drive down steel prices, forcing competitors out of business.
Answer: Option A
Step-by-step explanation:
Carnegie made monopoly in the economy of the United States in the field of iron and steel industry. He made monopoly by cutting down the costs and prices of the steel manufactured by him.
He almost owned everything which was required to make steel as a result of which he could cut down the prices. More over he also tried to reduce the inefficiencies in that factory and provided efficient work place to his employees. This also resulted in increasing the productivity of iron and steel.