Read the following excerpt from Andrew Carnegie's "Wealth."
Formerly articles were manufactured at the domestic
hearth or in small shops (that) formed part of the
household. The master and his apprentices worked side by
side, the latter living with the master, and therefore subject
to the same conditions. When these apprentices rose to be
masters, there was little or no change in their mode of life,
and they, in turn, educated in the same routine succeeding
apprentices."
What period was Carnegie describing?

A) The time after communism began

B) The era of utopian societies

C) The beginning of the free-enterprise system

D) The time before the Industrial Revolution