Final answer:
Jacob Riis uses the word 'slums' to describe the large number of children who are living in tenements. Riis's photographs and writings exposed the living conditions in these slums, leading to laws to improve tenements.
Step-by-step explanation:
Jacob Riis uses the word 'slums' to describe the large number of children who are living in tenements. He describes these areas as densely populated, dirty, and unsanitary. Riis's photographs and writings exposed the living conditions in these slums, leading to public awareness and eventually to laws to improve tenements.