Final answer:
The psychotherapy technique not developed by George Kelly is 'Social atom,' which is associated with Jacob Moreno. Kelly's techniques include Role playing, Rep test, and Fixed-role therapy.
Step-by-step explanation:
The technique that was not developed by George Kelly as a method used in psychotherapy is D) Social atom. The concept of social atom is associated with Jacob Moreno and refers to the smallest unit of a person's social universe. On the other hand, George Kelly was the psychologist who developed the Role playing, Rep test (Role Construct Repertory Test), and Fixed-role therapy. These were central to his personal construct theory of personality and are used within the framework of cognitive therapy.