are long- or short-term changes in population patterns or characteristics.

They went to leyden, holland

The answer should be b

What are the options?

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.