With Regard to Research on Schizophrenia Involving the Offspring of Twins

With regard to research on schizophrenia involving the offspring of twins, all of the following are accurate statements EXCEPT

A) the child of a schizophrenic identical twin has the same risk (17%) of having the disorder as the child of the non-schizophrenic identical twin.
B) the child of a non-schizophrenic fraternal twin has about a 2% risk of having the disorder.
C) a mentally healthy individual with a schizophrenic parent cannot pass on a genetic predisposition for the disorder to his or her offspring.
D) an individual can be free from schizophrenia but still be a "carrier."