Final answer:
The parents are showing 'unconditional positive regard' by expressing both disappointment and love, supporting their child irrespective of the test outcome, which aligns with Carl Rogers' humanistic psychology theories. Option C is correct.
Step-by-step explanation:
The humanistic concept being exhibited by the parents in the scenario is unconditional positive regard.
This term was coined by the humanistic psychologist Carl Rogers and it refers to accepting and supporting a person regardless of what they say or do.
The parents in the scenario demonstrate this by expressing their disappointment regarding the adolescent's study habits but also emphasize their unwavering love and support for their child.
This approach is believed to help individuals develop a healthier self-concept and encourages them to move towards self-actualization, which is the realization of one's full potential, another key humanistic concept introduced by Abraham Maslow.
Hence, option c is correct.