Jacob riis was most known for his late 19th century work in exposing the horrid living conditions a) on the great plains. b) on indian reservations. c) on southern plantations. d) in urban slums and ghettos.

The correct answer is D) in urban slums and ghettos.

Jacob Riis was most known for his late 19th-century work in exposing the horrid living conditions in urban slums and ghettos.

Jacob Riis (1849-1914) was a Danish immigrant that became a photographer and published a book of photographs he took in urban slums and ghettos of New York City. The name of the book was "How the Other Half Lives," showing the poverty and harsh conditions of these people. The book generated concern of people who started to participate in activist groups demanding better conditions for immigrants.

c. government control over the unsettled western lands