Concept:Gestalt psychology believes that the whole is greater than its parts, and its key proponents are Kohler, Koffka, and Wertheimer.
Explanation:Wolfgang Kohler studied problem-solving in chimpanzees and showed that they solve problems by insight.
Max Wertheimer founded Gestalt psychology and examined how diagrams aid students in solving geometry problems.
Kurt Koffka systematically applied Gestalt theory to perception and learning.
All three psychologists are associated with the Gestalt school of thought.
Therefore, each of them follows gestaltism.
Answer:Option D: All the above.