The economy grew more quickly during the Gilded Age than at any other time in US history. Two factors that caused this growth were

Steel production expanded rapidly during the Gilded Age, supporting growth in railroads, construction, and other industries. The value of manufactured goods also increased as factories produced more goods, so both factors contributed to economic growth. Choice C, a great increase in steel production and an increase in the value of manufactured goods, is correct.

AI-written and checked against the verified answer.