Describes the scientific study of the causes and prevention of crime and the rehabilitation and punishment of offenders

The correct answer is criminology.
Criminology is a branch of sociology, meaning that it deals with humans and societies in general, but particularly regarding crime. It studies why crime actually happens and what could be done to avoid it, as well as what should be done with offenders.

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.