Final answer:
Room 101, as described by O'Brien in '1984', is a room of punishment where individuals face their greatest fears, a psychological torture chamber used for control and breaking down resistance.
Step-by-step explanation:
According to O'Brien in George Orwell's novel 1984, Room 101 is the place where everybody confronts their worst fears or phobias, which means the correct answer is option 3) a room of punishment. The terror of Room 101 represents the Party's ultimate means of torture and control, where individuals are broken and made to betray their deepest loyalties or values. This psychological torture chamber is tailored to exploit the greatest fears of the prisoners, which Orwell depicts as the worst thing in the world for each person.