What caused the great waves of immigration from Europe to the United States in the mid-1840's? a. the yearning for liberty
b. the monarchy of Europe ordering people to leave
c. the influence of Karl Marx
d. the failure of Europe's crops

An informal structure in a bureaucracy would be something like so-called "office politics". where there's a formal structure set up for the organization, but then an informal subculture as well that has a way of organizing the bureaucracy further. this can be positive because it sets up an added degree of organization, albeit informal, within the bureaucracy.