Adoption Studies of Schizophrenia Have Found That Schizophrenia ________ When

Adoption studies of schizophrenia have found that schizophrenia ________ when they are raised by normal adoptive parents.

A) does not occur among children of schizophrenic biological parents nor among children of normal biological parents
B) occurs more frequently among children of schizophrenic biological parents than among children of normal biological parents
C) occurs more frequently among children of normal biological parents than among children whose parents had schizophrenia
D) occurs equally among the children of normal parents and among the children whose parents had schizophrenia