The correct answer would be A) Early 1900's.
Even though the fight to end child labor starts in the late 1800's, it gains a significant amount of momentum during the Progressive Era which takes place in the early 1900's. A perfect example of this can be seen with the development of the National Child Labor Committee being formed in 1904. This private organization was formed to help advocate for children who were working in American industry during the early 1900's. Also during the early 1900's, more laws were passed to protect child labor. This includes the Fair Labor Standards Act of the 1930's.
