As the Nineteenth Century Progressed, the Ruhr Region of Europe

As the nineteenth century progressed, the Ruhr region of Europe developed an unusually diverse ethnic character due to which of the following factors?

A) The demand for labour brought immigrants from all over Europe.
B) Industrial innovations attracted outside visitors.
C) The coal and iron ore deposits encouraged many industries to be set up.
D) Landscape changes generated considerable interest in the area.
E) None of the above