Push and pull factors affect not onlu how people move, but also how natural resources and ideas move. why is this true?

The answer is the third one or c

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.