What the question is asking, I believe, is what will best communicate the idea and persuade people the most.
The answer, I believe is the picture of the sweaty, dirty, exahusted children in coal mines.
The first choice doesn't work, obviously, because there is nothing mentioned about child labor.
The second choice works word wise, but it has no visual. You are also hearing it through someone else's words, as if third person.
The fifth choice would be correct, BUT the fourth choice is better. With the fifth, you see children working. That's sad. But, with the fourth, you not only see the children working, but tired, exahusted, and dirty. That truly communicates how horrible child labor is.
Hope I helped.