The answer is: C. apprenticeship
During apprenticeship programs, students could come directly to a certain working site and observe directly how a real life job would look like with their own eyes.
Not all apprenticeship is paid (even though some companies do offer some sort of benefit for their apprentices).
During the apprentice program, the students would be guided by mentors that consist of the people who already had more experience than them in their specific field. From this mentor, students could gain new knowledge that they cannot usually found in schools/university.