Which of these was the most noticeable symbol of the "iron curtain"?
a) great wall
b) berlin wall
c) 38th parallel
d) 17th parallel

The correct answer is b

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.