Final answer:
Jacob Riis' book How the Other Half Lives documented A) The poverty and squalor of the slums of New York City in the late 19th century. Through striking photography and gripping journalism, Riis highlighted the living conditions of the urban poor which led to early housing reform laws.
Step-by-step explanation:
Jacob Riis' book How the Other Half Lives documented A) The poverty and squalor of the slums of New York City in the late 19th century. Riis, an immigrant and reporter for the New York Tribune, used photography and journalism to reveal the stark conditions in which the city's working poor lived. His photographs, like the 1890 image of children sleeping in Mulberry Street, exposed the harsh realities of tenement houses and the densely populated slums. Riis' work brought the living conditions of the urban poor to the attention of the wider American public and led to some of the nation's first laws to improve tenement housing.
His book included photographs and descriptions that highlighted the dire situation in urban slums and tenements, filled predominantly by immigrant families. Through his work, Riis became an advocate for social reform, seeking to elicit compassion and action from the middle and upper classes to improve the dangerous and unsanitary living conditions that he documented. The power of Riis' photojournalism, accompanied by his vivid storytelling, made a significant impact and spurred conversations about urban poverty and housing reform.