Industrial Enterprises Grew to Unprecedented Sizes in the Late Nineteenth

Industrial enterprises grew to unprecedented sizes in the late nineteenth and early twentieth centuries, partly because

A) the population began to leave the cities to live in rural areas.
B) markets were being closed all over the world.
C) the American economy became isolated and primarily domestic.
D) some new technologies required huge levels of investment and manpower.
E) the government began to regulate industrial advancement.