Which of the Following Findings Presents a Serious Challenge to the Theory

Which of the following findings presents a serious challenge to the theory of schizophrenia that proposes an excess amount of dopamine to be at the core of this disorder?

A) Antipsychotic drugs relieve the symptoms of both drug psychoses and the psychosis of schizophrenia.
B) Homovanillic acid,the major metabolite of dopamine,is not present in greater amounts in schizophrenics.
C) Positive symptoms of schizophrenia are reduced by antipsychotic drugs more than negative symptoms.
D) None of the above represents a challenge to the dopamine activity theory.