Which type of government is described by the characteristics listed below? centralized; government in one location; one authority

The correct answer is "unitary", a unitary government is somehow the opposite of a federal government: it has one, central government in one location that decides over all the relevant issues and the parts of the country don't have (even a small, relative) autonomy

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.