Which development improve working conditions in many mines and factories during the late 1800s. 1) the formation of monopolies. 2) the growth of labor unions. 3) the rise of the middle class. 4) the introduction of the assembly line.

a agree i agree becuase it is very importnat for example it can tlel you about your past for exmaple   the first culture was the semerians which people are sitll tryignt o uncover there secrets the wall is just anohter treasure that has thousnads of secrets in it to be uncovered