Why Have There Been Criticisms of Research Showing an Association

Why have there been criticisms of research showing an association between schizophrenia and brain damage prior to the onset of the symptoms?

A) Reports rely on the memories of relatives and patients about details of the injury.
B) The samples used in these studies included too few men to generalize well.
C) There is a failure to control adequately for substance use in these reports.
D) Reports do not take into account damage to brain areas associated with other disorders.