Final answer:
According to Carl Rogers' humanistic psychology, a fully functioning person is characterized by openness to new experiences, exhibiting a growth-oriented mindset and congruence between their real self and ideal self.
Step-by-step explanation:
The characteristic of the fully functioning person according to the psychology of Carl Rogers is C) Openness to new experiences. Rogers, a humanistic psychologist, posited that a fully functioning person exhibits congruence between their real self and ideal self. Such individuals are open to experiences, embody a sense of freedom, and possess the ability to live harmoniously with a full awareness of their experiences. They are characterized by a tendency towards growth and fulfillment of their potential, and they live a life that is rich, full, and exciting. This openness also includes a willingness to experience each moment fully, not being shackled by conformity or societal expectations, thus showing a clear distinction from rigid conformity to external standards.