According to the Author of This Textbook, an Appropriate Answer

According to the author of this textbook, an appropriate answer to the question "Do we still need theory?" is:

A) Theory is most relevant for the client, not the therapist.
B) Theories prevent therapists from using a systematic way for dealing with the wide range of difficulties clients can bring.
C) Theories are important because they are the vehicles through which the common factors do their work.
D) Theories do not allow therapists to take into consideration unique issues related to diversity.