Which of the Following Statements Is True About Prior Research

Which of the following statements is true about prior research on practitioner effectiveness?

A) It can be influenced by the type of intervention employed as well as practitioner-client relationship factors.
B) All the credible evidence shows that it is influenced only by the type of intervention employed.
C) All the credible evidence shows that it is influenced only by the quality of the practitioner-client relationship.
D) None of the above.