Based on Current Research, Which Statement Can Be Justified

Based on current research, which statement can be justified?

A) Genetics play such a strong role, they are a sufficient condition for schizophrenia.
B) Genetics increase a person's vulnerability to develop schizophrenia.
C) Genetics may not be sufficient for schizophrenia, but everyone who develops schizophrenia must have some number of "schizophrenia genes."
D) Genetics cannot play a significant role in the cause of schizophrenia because most people with the disorder have no close relatives who have it.