What is the main subject of the book "How the Other Half Lives"?

The main subject of "How the Other Half Lives," written by Jacob Riis, focuses on the struggles of poor urban immigrants during the late 19th century, particularly in New York City. Riis, a journalist and social reformer, used vivid photography and compelling narratives to document the harsh living conditions and challenges faced by the impoverished populations in tenement housing. His work aimed to raise awareness about the plight of these immigrants, advocating for social reform and better living conditions.

While the other options touch on aspects of societal issues, they do not accurately capture the core focus of Riis's work. Urban elites and their lifestyles are not the subject of the book, nor does it primarily examine rural lifestyles or wealth in a more general context. Instead, it zeroes in on the specific experiences and hardships of those living in poverty in urban environments, making option B the correct answer.