Research Studies Focusing on Genetic Factors in Schizophrenia Have Found

Research studies focusing on genetic factors in schizophrenia have found that

A) an individual with a schizophrenic identical twin has the highest risk factor (almost 50%) of developing schizophrenia.
B) in family studies of schizophrenia, the genetic influence can be separated from the environmental impact.
C) if one person in a family has a particular subtype of schizophrenia, for example, paranoid, the other family members inherit a predisposition for that subtype only.
D) the more severe a parent's schizophrenic disorder, the less likely the children are to develop it.