There Is a New Trend to Focus on Dopamine Receptor

There is a new trend to focus on dopamine receptor sensitivity rather than on dopamine itself because

A) there is only one type of dopamine receptor.
B) there is strong evidence that people with schizophrenia have used too many drugs.
C) there is strong evidence that people with schizophrenia have too much dopamine.
D) there is no strong evidence that people with schizophrenia have too much dopamine.