Which of the Following Would Be the Best Definition of Psychotherapy

Which of the following would be the best definition of psychotherapy?

A) The use of drugs and other medical techniques to alleviate the symptoms of emotional disturbance.
B) A technique in which improvement is caused not by the process but by the client's expectation.
C) A psychological technique used to facilitate positive changes in a person's personality, behavior, or personal adjustment.
D) A psychological technique in which a group of people who share a particular type of problem provide mutual support and counseling for one another.