Which "schizophrenia fact" is correct? select one: a. when one identical twin is affected with schizophrenia the other most certainly will be affected. b. copy number variants appear to play the most important role in genetic risk for schizophrenia. c. when schizophrenia has more genetic influence, its onset begins in very early childhood. d. because the phenotype of schizophrenia is so obvious, diagnosis and inheritance risk are the most easily determined of all the psychiatric disorders?