Final answer:
Humanism is the theoretical perspective that led to the new subfield of psychology known as positive psychology.
Step-by-step explanation:
The theoretical perspective that led to the new subfield of psychology known as positive psychology is c) Humanism. Humanism is a perspective within psychology that emphasizes the potential for good that is innate to all humans. It focuses on personal control, intentionality, and a true predisposition for "good" as important for our self-concept and behavior.