Answer:
C - He focused on how the children's innocence was taken away by having them work dangerous jobs.
Step-by-step explanation:
Chimney sweeping was considered a dangerous job because of soot inhalation. Especially if children are being forced into labor, I doubt they'd have much innocence.
The part where Tom's dreaming and an angel comes to release them shows that he and all the other boys were born to work and be sold off. Even in the first paragraph, he says his mom dies and his father sold him off.