If Heredity Alone Is Responsible for a Disorder Such as Schizophrenia

If heredity alone is responsible for a disorder such as schizophrenia, one would expect that

A) monozygotic twins should be 100% concordant for the trait.
B) children of schizophrenic mothers should have at least a 75% chance of being schizophrenic themselves.
C) monozygotic twins should be 50% concordant for the trait.
D) schizophrenia should be present at birth.