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 era of utopian societies

b. the beginning of the free-enterprise system

c. the time after communism began

d. the time before the industrial revolution