Please confirm that this awnser is right please only awnser if you are 100% sure it’s right ( I will brainlist) and

Isay b but i'm not sure. 

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.