Final answer:
The belief that a supportive environment leads to the full potential development aligns with Humanistic Psychology (C), championed by Abraham Maslow and Carl Rogers.
Step-by-step explanation:
The subject who believed that with a supportive and stimulating environment, we automatically develop into our full potential is C) Humanistic Psychology. This approach, stemming from dissatisfaction with the more deterministic perspectives of psychoanalysis and behaviorism, focuses on the innate potential for good and growth in all humans. It underscores personal control, intentionality, and intrinsic growth tendencies. Psychologists like Abraham Maslow and Carl Rogers are prominent figures in humanistic psychology, with theories that stress the importance of achieving self-actualization and fulfilling one's fullest potential.