The correct answer is C) Working poor.
The goal of writing "How the other half lives" was for Jacob Riis to point out the poor living conditions of industrial workers. His focus included immigrant industrial workers living in large cities (like New York). Besides his writing, the pictures provided by Riis tell a story of families living in extremely unsanitary and small quarters.
The pictures of these tenements help American readers to understand what life is like for immigrants. Riis hoped to inspire citizens to act and help to develop a solution to this situation.