Which of the following statements is true of psychological dependence as a characteristic of substance use?
A. It is the toxicity resulting from the behavioral effects of a drug.
B. It is the reduced effect of a drug after repeated use.
C. It is indicated by the presence of a withdrawal syndrome, implying that the body has become adapted to the drug's presence.
D. It is indicated by the frequency of using a drug or by the amount of time or effort an individual spends in drug-seeking behavior.