A Psychologist Discovers That the Blood of Patients with Schizophrenia

Multiple Choice

A psychologist discovers that the blood of patients with schizophrenia contains a certain chemical not found in the general population.This means that

A) this chemical causes a person to develop schizophrenia.
B) having schizophrenia causes this chemical to form in a person's blood.
C) both schizophrenia and the chemical are caused by some unknown third factor, such as the typical diet in mental hospitals.
D) the chemical and schizophrenia are related, but no causal relationship has been established.