Both of Mary's Parents Have Been Diagnosed with Schizophrenia

Both of Mary's parents have been diagnosed with schizophrenia. Bob has an identical twin, who has schizophrenia. Who is more likely to develop schizophrenia and why?

A) Bob, because he is male and has a family history of schizophrenia.
B) Mary, because all of her genes come from her parents and they both have the disease.
C) Bob, because he has inherited the same susceptibility that his twin is expressing.
D) Mary, because females are more susceptible than males to the genetic forms of schizophrenia.