During the Gilded Age, most laborers were considered to be in?

A. the middle class.

B. the upper class.

C. the ruling class.

D. the working class.

D. working class. Much of that huge population surge was made up of poor European immigrants who lived in overcrowded slums on the West and South Sides, doing grueling work for low wages in the city's stockyards, factories, and on the railroads.