Answer:
The correct option is A. Ben is part of the criminal university
Ben is using his skills to make friends and run sports betting ring in prison. Based on such a circumstance, one might infer that Ben is a part of the criminal university. The idea of sport betting rings in prison is very common and it also brings a huge amount of money for some people.
Other options, like option B is not correct because Ben is not teaching any classes in the prison.