Why Was "The City" the Focus of Progressive Politics

Why was "the city" the focus of progressive politics?

A) The mostly urban immigrant populations wielded significant political clout there.
B) Populists had largely solved the problems that had plagued rural Americans.
C) The overwhelming majority of Americans lived in cities.
D) Urban populations experienced the most dramatic growth and the most significant changes.
E) Progressives were particularly fond of new urban entertainments like dance halls and nickelodeons.