The Decrease in Popularity of Gestalt Therapy May Have Been

The decrease in popularity of gestalt therapy may have been due to:

A) the fact that Fritz Perls was not interested in testing his ideas through research.
B) the strong psychoanalytic influence on his approach to therapy.
C) the personal conflict that he had with the more popular Carl Rogers.
D) extensive research that found that the techniques of gestalt therapy are ineffective.