Which Statement About Token Economies Is NOT Supported by Research

Which statement about token economies is NOT supported by research?

A) Many studies of effectiveness do not include a control group, confounding the treatment with attention.
B) Although token economy programs can change patients' delusional statements, they may not be changing delusional thoughts.
C) Token economy programs do not change the behavior of the most severely ill patients.
D) It is difficult for patients to make the transition from a token economy program to the community.