How Are the Effects of Drugs Influenced by Psychological Factors

 How are the effects of drugs influenced by psychological factors? 

A) If you believe a drug will not affect you, it probably will not.
B) When taken by mentally ill people, drugs usually have different effects than they would in mentally healthy people.
C) People who expect a drug to influence them in a particular way are more likely to change their behavior to fit the expectation.
D) The effects of drugs are influenced by psychological factors only in people who are already addicted.